Apparatus and method for control of a vehicle

ABSTRACT

An apparatus and method for transporting a payload over a surface is provided. A vehicle supports a payload with a support partially enclosed by an enclosure. Two laterally disposed ground-contacting elements are coupled to at least one of the enclosure or support. A motorized drive is coupled to the ground-contacting elements. A controller coupled to the drive governs the operation of the drive at least in response to the position of the center of gravity of the vehicle to dynamically control balancing of the vehicle.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/266,170 filed Nov. 6, 2008, the entire content of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to control of vehicles, and inparticular, controlling vehicle motion.

BACKGROUND OF THE INVENTION

A wide range of vehicles and methods are known for transporting humansubjects. Typically, such vehicles rely upon static stability and aredesigned for stability under all foreseen conditions of placement oftheir ground-contacting members with an underlying surface. For example,a gravity vector acting on the center of gravity of an automobile passesbetween the points of ground contact of the automobile's wheels and thesuspension of the automobile keeps all wheels on the ground at all timesmaking the automobile stable. Although, there are conditions (e.g.,increase or decrease in speed, sharp turns and steep slopes) which causeotherwise stable vehicles to become unstable.

A dynamically stabilized vehicle, also known as a balancing vehicle, isa type of vehicle that has a control system that actively maintains thestability of the vehicle while the vehicle is operating. In a vehiclethat has only two laterally-disposed wheels, for example, the controlsystem maintains the fore-aft stability of the vehicle by continuouslysensing the orientation of the vehicle, determining the correctiveaction necessary to maintain stability, and commanding the wheel motorsto make the corrective action. If the vehicle losses the ability tomaintain stability, such as through the failure of a component or a lackof sufficient power, the human subject can experience a sudden loss ofbalance.

For vehicles that maintain a stable footprint, coupling between steeringcontrol and control of the forward motion of the vehicles is less of aconcern. Under typical road conditions, stability is maintained byvirtue of the wheels being in contact with the ground throughout thecourse of a turn and while accelerating and decelerating. In a balancingvehicle with two laterally disposed wheels, however, any torque appliedto one or more wheels affects the stability of the vehicle.

In prior art systems, such as the self balancing vehicles shown in U.S.Pat. No. 5,871,091 personal vehicles may be self-propelled anduser-guidable, and, further, may entail stabilization in one or both ofthe fore-aft or left-right planes, such as when no more than two wheelsare in ground contact at a time. Vehicles of this sort may be operatedin a mode in which motion of the vehicle, including acceleration (bothlinear and turning), is commanded partially or entirely by leaning ofthe vehicle as caused by a subject riding the vehicle. Several suchvehicles are described in U.S. application Ser. No. 08/384,705 which isincorporated herein by reference.

Such balancing vehicles may lack static stability. Referring, forexample, to FIG. 1A, wherein a prior art personal transporter is shownand designated generally by numeral 18, a subject 10 stands on a supportplatform 12 and holds a grip 14 on a handle 16 attached to the platform12, so that the vehicle 18 of this embodiment may be operated in amanner analogous to a scooter. A control loop may be provided so thatleaning of the subject results in leaning of the platform which, inturn, results in the application of torque to wheel 20 about axle 22thereby causing an acceleration of the vehicle. Vehicle 18, however, isstatically unstable, and, absent operation of the control loop tomaintain dynamic stability, subject 10 will no longer be supported in astanding position and can fall from platform 12. Another prior artbalancing vehicle is shown in FIG. 1B and designated generally bynumeral 24. Personal vehicle 24 shares the characteristics of vehicle 18of FIG. 1A, namely a support platform 12 for supporting subject 10 andgrip 14 on handle 16 attached to platform 12, so that the vehicle 24 ofthis embodiment may also be operated in a manner analogous to a scooter.FIG. 1B shows that while vehicle 24 may have clusters 26 each having aplurality of wheels 28, vehicle 24 remains statically unstable and,absent operation of a control loop to maintain dynamic stability,subject 10 will no longer be supported in a standing position and mayfall from platform 12.

A standing rider 10 of the vehicle 30 places his feet on the platformand shifts weight back and forth in a relatively wide and flat path 33.The slight amount of strength that is needed to resist gravity andinertia in transversing this arc is well within the strength andcoordination of an average user's muscles. The center of gravity of thevehicle and rider 35 moves in an arcuate fashion as the rider leanseither forward or backward. When a seat is added to such a vehicle,movement of the center of gravity in the manner described above may nolonger be possible and an alternative mechanism for shifting the centerof gravity is required. The mechanism needs to provide adequate range ofmotion while allowing the rider to resist gravity and inertia.

SUMMARY OF THE INVENTION

The invention, in one aspect, features a vehicle for transporting apayload over a surface. The vehicle includes a support for supporting apayload and an enclosure for at least partially enclosing the payload.The vehicle also includes two laterally disposed ground-contactingelements (e.g., wheels, tracks, rollers, legs) coupled to at least oneof the enclosure or the support. The vehicle also includes a drivecoupled to the ground-contacting elements. The vehicle also includes acontroller coupled to the drive, for governing the operation of thedrive at least in response to the position of the center of gravity ofthe vehicle to dynamically control balancing of the vehicle.

In some embodiments, the drive propels the ground-contacting elementsalong the ground. In some embodiments, the enclosure is coupled to thesupport. In some embodiments, the vehicle includes a structure couplingthe support and the enclosure to the ground-contacting elements, thestructure allows for variation in the position of the center of gravity.In some embodiments, the position of the center of gravity varies in oneor more of the fore-aft, lateral and vertical planes of the vehicle. Insome embodiments, the structure includes rails allowing the enclosureand support to slide with respect to the ground-contacting elements. Insome embodiments, the structure includes a pivot mechanism coupling thesupport and enclosure to the ground-contacting elements allowing theenclosure and support to pivot with respect to the ground-contactingelements.

In some embodiments, the payload is a human subject and the vehicleincludes an input device, the human subject pushes or pulls the inputdevice allowing the human subject, support and enclosure to move withrespect to the ground-contacting elements.

In some embodiments, the vehicle includes one or more (e.g., two)four-bar linkages, each four-bar linkage coupling a ground-contactingelement to the support and the enclosure, allowing the enclosure andsupport to move relative to the ground-contacting elements. In someembodiments, the enclosure is coupled to the ground-contacting elements.

In some embodiments, the vehicle includes a structure coupling thesupport to the enclosure and ground-contacting elements, the structureallows for variation in the position of the center of gravity. In someembodiments, the structure includes rails allowing the support to slide(e.g., fore and aft) with respect to the enclosure and theground-contacting elements. In some embodiments, the structure includesa pivot mechanism coupling the support to the enclosure andground-contacting elements, allowing the support to pivot with respectto the enclosure and ground-contacting elements.

In some embodiments, the vehicle includes two four-bar linkages, eachfour-bar linkage coupling the support to the enclosure and theground-contacting elements, and allowing the support to move relative tothe ground-contacting elements. In some embodiments, the payload is ahuman subject and the structure includes an input device, the humansubject pushes or pulls relative to the input device allowing the humansubject and support to move with respect to the enclosure andground-contacting elements.

In some embodiments, the vehicle includes an actuator that controls theposition of the center of gravity of one or more of the support, payloador enclosure relative to the ground-contacting elements. In someembodiments, the vehicle is controlled based on a selected operationmode. In some embodiments, the operation mode is a remote controlledmode or the payload is a human subject and the operation mode is a humansubject controlled mode. In some embodiments, the payload is a humansubject that applies pressure on a foot member coupled to the vehicle(e.g., platform, support or enclosure) to decelerate the vehicle. Insome embodiments, the human subject applies pressure on the foot membercoupled to the vehicle to accelerate the vehicle.

In some embodiments, a shift of the position of the center of gravityrearward causes a deceleration (e.g., if initially moving forward) ofthe vehicle. In some embodiments, a shift of the position of the centerof gravity rearward causes a rearward acceleration (e.g., if initiallystopped or moving rearward) of the vehicle. In some embodiments, a shiftof the position of the center of gravity forward causes a forwardacceleration of the vehicle. In some embodiments, a shift of theposition of the center of gravity forward causes a deceleration of thevehicle when initially traveling rearward. In some embodiments, thevehicle includes a stabilizer ground-contacting element positioned onthe vehicle to statically stabilize the vehicle (e.g., when not beingdynamically stabilized). In some embodiments, the stabilizerground-contacting element is retractable. In some embodiments, thestabilizer ground-contacting element includes a sensor for detecting atleast one of the a) stabilizer ground-contacting element contacting theground or b) force applied between the stabilizer ground-contactingelement and the ground. In some embodiments, the stabilizerground-contacting element includes one or more wheels, skids, balls orposts.

In some embodiments, the vehicle includes one or more sensors fordetecting a change in the position of the center of gravity of thevehicle. In some embodiments, the one or more sensors is one or more ofa force sensor, position sensor, pitch sensor or pitch rate sensor.

In some embodiments, a start mode that is triggered by a change in theposition of the center of gravity of the vehicle, the change in theposition of the center of gravity initiating dynamic stabilization ofthe balancing vehicle such that the vehicle is no longer stabilized by astabilizer ground-contacting element. In some embodiments, thestabilizer ground-contacting element is positioned towards the front ofthe vehicle and the position of the center of gravity shifts rearwardto, for example, trigger a start mode. In some embodiments, thestabilizer ground-contacting element is positioned rearward of thevehicle and the position of the center of gravity shifts forward to, forexample, trigger a start mode. In some embodiments, a shift of theposition of the center of gravity of the vehicle beyond a thresholdtriggers a stop mode that decelerates the vehicle.

In some embodiments, the payload is a human subject and the vehicleincludes an input device, the input device coupled to the vehicle by alinkage such that the vehicle accelerates forward (or deceleratesrearward) when the human subject pushes the input device forward and thevehicle decelerates forward (or accelerates rearward) when the humansubject pulls the input device rearward.

In some embodiments, the drive delivers power to the ground-contactingelements to cause rotation of the ground-contacting elements todynamically control balancing of the vehicle. In some embodiments, thedrive is a motorized drive. In some embodiments, the drive moves theground-contacting elements fore and aft of the vehicle to dynamicallycontrol balancing of the vehicle.

In some embodiments, the vehicle includes a second drive for deliveringpower to the ground-contacting elements to propel (e.g., cause rotationof the ground-contacting elements) the vehicle for and aft. In someembodiments, the vehicle includes an internal combustion engine, pedal,or crank coupled to the second drive for delivering power to theground-contacting elements to, for example, cause rotation of theground-contacting elements to propel the vehicle for and aft

The invention, in another aspect, features a method for transporting apayload over a surface with a vehicle. The method involves supporting apayload with a support and at least partially enclosing the support withan enclosure. The method also involves controlling operation of a drivein response to position of the center of gravity of the vehicle todynamically control balancing of the vehicle, wherein the drive iscoupled to two laterally disposed ground-contacting elements coupled toat least one of the enclosure or support.

In some embodiments, the delivered power is in response to attitude(e.g., pitch) of the vehicle. In some embodiments, the enclosure iscoupled to the support and the support and enclosure move relative tothe ground-contacting elements to change the position of the center ofgravity of the vehicle. In some embodiments, the enclosure is coupled tothe ground-contacting elements and the support moves relative to theenclosure and ground-contacting elements to change the position of thecenter of gravity of the vehicle. In some embodiments, the support andenclosure slide relative to the ground-contacting elements. In someembodiments, the support slides relative to the enclosure and theground-contacting elements. In some embodiments, the support andenclosure pivot relative to the ground-contacting elements. In someembodiments, the support pivots relative to the enclosure and theground-contacting elements.

In some embodiments, the method involves applying pressure to a footmember coupled to the vehicle to decelerate the vehicle. In someembodiments, the method involves shifting the position of the center ofgravity rearward to cause a deceleration of the balancing vehicle. Insome embodiments, the method involves shifting the position of thecenter of gravity forward to cause an acceleration of the balancingvehicle. In some embodiments, the method involves shifting the center ofgravity rearward to cause an acceleration of the balancing vehicle. Insome embodiments, the method involves stabilizing the balancing vehiclewith a stabilizer ground-contacting element positioned on the vehicle.In some embodiments, the method involves retracting the stabilizerground-contacting element when the vehicle is dynamically balanced.

In some embodiments, the method involves triggering a start mode when asensor mounted on the vehicle detects a change in the position of thecenter of gravity shift and initiating dynamic stabilization of thevehicle. In some embodiments, the method involves shifting the positionof the center of gravity rearward to initiate dynamic stabilization ofthe vehicle. In some embodiments, the method involves shifting theposition of the center of gravity forward to initiate dynamicstabilization of the vehicle. In some embodiments, the method involvestriggering a stop mode of the vehicle by shifting the position of thecenter of gravity of the vehicle beyond a threshold and decelerating thebalancing vehicle.

In some embodiments, the method involves applying pressure to a footmember coupled to at least one of the platform or enclosure to move theposition of the center of gravity rearward. In some embodiments, therelative position of the payload to the ground-contacting elements is aninput to the controller. In some embodiments, the input is added to orsubtracted from commanded acceleration or deceleration of the vehicle bychanging desired pitch of the vehicle and shifting the position of thecenter of gravity of the vehicle. In some embodiments, the inputmodifies desired pitch of a speed limiting algorithm used to controlspeed of the vehicle.

In some embodiments, the method involves delivering power from the driveto the ground-contacting elements to cause rotation of theground-contacting elements to dynamically control balancing of thevehicle. The method also involves the drive moves the ground-contactingelements fore and aft of the vehicle to dynamically control balancing ofthe vehicle. In some embodiments, the method includes delivering powerfrom a second drive to the ground-contacting elements to cause rotationof the ground-contacting elements to move the vehicle fore and aft.

The invention, in another aspect, features a vehicle for transporting apayload over a surface. The vehicle includes a support for supporting apayload and an enclosure for at least partially enclosing the payload.The vehicle also includes two laterally disposed ground-contactingelements coupled to at least one of the enclosure or the support. Thevehicle also includes a drive coupled to the ground-contacting elements.The vehicle also includes means for governing the operation of the driveat least in response to position of the center of gravity and/or tilingof the vehicle to dynamically control balancing of the vehicle.

The invention, in another aspect, features a vehicle for transporting apayload over a surface. The vehicle includes a support for supporting apayload and an enclosure for at least partially enclosing the payload.The vehicle also includes two laterally disposed ground-contactingelements coupled to at least one of the enclosure or the support. Thevehicle also includes a first drive coupled to the ground-contactingelements. The vehicle also includes a controller coupled to the firstdrive, for governing the operation of the first drive at least inresponse to the position of the center of gravity of the vehicle to movethe ground-contacting elements fore and aft of the vehicle todynamically control balancing of the vehicle. The vehicle also includesa second drive coupled to the ground-contacting elements to deliverpower to the ground-contacting elements to propel the vehicle for andaft.

In some embodiments, the vehicle includes an internal combustion enginecoupled to the second drive for delivering power to theground-contacting elements. In some embodiments, the vehicle includesrails coupled to the ground-contacting elements allowing the first driveto command the ground-contacting elements to move fore and aft of thevehicle to dynamically control balancing of the vehicle.

The invention, in another aspect, features a method for transporting apayload over a surface with a vehicle. The method involves supporting apayload with a support and at least partially enclosing the support withan enclosure. The method also involves controlling operation of a firstdrive, coupled to at least one of the enclosure or support, in responseto position of the center of gravity of the vehicle to move theground-contacting elements fore and aft of the vehicle to dynamicallycontrol balancing of the vehicle. The method also involves controllingoperation of a second drive coupled to the two laterally disposedground-contacting elements to deliver power to the ground-contactingelements to propel the vehicle fore and aft.

The invention, in another aspect, features a device for transporting ahuman subject over a surface is disclosed. The device is a dynamicallybalancing vehicle having a control loop for providing balance. Thedevice includes a platform defining a fore-aft plane. The platformsupports a payload including the human subject. A ground-contactingmodule is included which may be one or more wheels. Theground-contacting member is movably coupled to the platform. The deviceand any load on the device have a center of gravity that is defined withrespect to the ground-contacting member. The device further includes asupport. The support may be a seat for supporting the subject and thesupport is coupled to the platform in such a manner as to permitvariation of the position of the center of gravity in the fore-aft planeby translation and rotation of at least a portion of the support. Thetranslation and rotation of at least a portion of the support aremechanically coupled in one embodiment.

The transportation device further includes a drive which is coupled tothe ground-contacting module and which delivers power to theground-contacting module in a manner responsive to the position of thecenter of gravity. The drive supplies force so as to balance thevehicle. In one embodiment, the support rotates about a virtual pivotpoint which lies above the support. The structure of the support allowsthe support to rock about an arc or other path.

The support may include a mechanical linkage such as a four-bar linkage.In one embodiment, each bar of the four-bar linkage is coupled togetherwith pivots. A structure (e.g., a fifth bar) may be included for holdinga seat. The structure is attached at one of the pivots of the four-barlinkage. In another embodiment, the structure is attached to one of thebars of the four-bar linkage. In one embodiment, the four-bar linkageforms a parallelogram and changes shape as a user of the vehicle moveson the seat shifting the center of gravity.

In one embodiment, the device includes pressure sensors for activatingthe drive and causing the control loop to become active when the driveror payload is present. The pressure sensors may be placed in theplatform for activation or the pressure sensors may be placed in theseat. In yet another embodiment, a mechanical contact is attached to thesupport which contacts the pressure sensors that are coupled to theplatform.

In another embodiment of the invention, the support includes a seat thatis slideably mounted. The support includes one or more rails forallowing the seat to slide. The seat need not be capable of rotationabout a pitch axis of the vehicle in such an embodiment, but does allowfor the user to change the center of gravity for controlling thevehicle. In another variation of the sliding seat, the sliding seat doesrotate about the pitch axis of the vehicle. As the seat slides along therails a mechanism causes the seat to rotate about the pitch axis of thevehicle. In one embodiment, the rails include one or more sprockets thatengage with protrusions that are coupled to the seat and thus causerotation as the seat is rolled on the rails. In another embodiment, thesupport may include one or more pulleys that assist the seat in slidingalong the one or more rails. In yet another embodiment, the seat iscoupled to friction wheels that ride on a friction surface.

In one embodiment, the support includes a convex radial base that allowsthe support to rock in response to a user shifting his weight. Theconvex radial base may be coupled to the platform at a pivot point thattranslates fore and aft with the motion of the seat. In otherembodiments, the convex radial base may have different radii ofcurvature along its convex surface.

In certain embodiments, the support may include a damper to resistmotion of the slide and damp unwanted control system oscillations. Inone embodiment, the support preferably returns to a position, such thatthe vehicle remains substantially stationary when no force is applied tothe support. In such an embodiment, the vehicle may still move slightlyas the control loop balances the vehicle.

In some embodiments, a controller is either coupled to the drive or partof the drive and the controller is part of a control loop which isresponsive to changes in the tilt angle of the vehicle. In certainembodiments, the seat may be coupled to the platform by a universalpivot. In another embodiment, the seat is coupled to a control stalk.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying drawings, in which:

FIG. 1A is a side view of a prior art dynamically balancing vehicle ofthe type of which an embodiment of the invention may be advantageouslyemployed.

FIG. 1B is a side view of a further prior art dynamically balancingvehicle of the type of which an embodiment of the invention may beadvantageously employed.

FIGS. 2A and 2B are a prior art dynamically balancing vehicle having aplatform that rotates in an arc.

FIG. 3 shows a dynamically balancing vehicle having a seat.

FIG. 3A shows a dynamically balancing vehicle in which the seat iscoupled to a control stalk.

FIG. 3B shows a dynamically balancing vehicle in which the seat iscoupled to the platform by a pivot.

FIG. 3C shows a dynamically balancing vehicle in which the seat isslideably mounted.

FIG. 3D shows a dynamically balancing vehicle having a seat.

FIG. 4A shows the seat of the dynamically balancing vehicle mounted on afour-bar linkage.

FIG. 4B shows one position of the four-bar linkage as would occur if arider leaned backwards shifting the center of gravity in the aftdirection.

FIG. 4C shows that the four-bar linkage simulates a rocking motion suchthat there is translation and rotation of the seat.

FIG. 4D shows the center of gravity translating in a straight line whilethe seat both translates and rotates.

FIG. 4E shows a bar linkage mechanism for translation and rotationwherein one or more bars are flexible.

FIG. 5A is an embodiment of the dynamically balancing vehicle in whichthe seat is attached to a bar via a pivot.

FIG. 5B is an embodiment that shows the seat attached to a slider abouta pivot point wherein pulleys help to control rotation.

FIG. 5C shows a seat that is coupled to a slider that rides on at leastpartially curved rails.

FIG. 5D shows a seat coupled to a track which includes friction wheelswherein the seat both translates and rotates.

FIG. 5E shows a support structure having a plurality of pins which willengage with recesses in the platform.

FIG. 6 shows a side view of an embodiment of the dynamically balancingvehicle with a detachable rocker seat.

FIG. 6A shows the support structure attached to the platform via asimple cable under tension.

FIG. 6B shows the support structure including a series of teeth on thebottom arced surface and also on the platform.

FIG. 6C shows the support structure coupled to the platform about apivot point.

FIG. 7A shows a folding seat which can be attached to a dynamicallybalancing vehicle wherein the seat is positioned as if a rider issitting on the seat.

FIG. 7B shows a rider sitting on the folding seat.

FIG. 7C shows the position of the folding seat when a riderengages/disengages with the vehicle.

FIG. 7D shows an embodiment of a dynamically balancing vehicle havingknee supports.

FIGS. 8 and 8A show an embodiment of a support structure which includesboth translational and rotational mechanical actuators.

FIG. 9 is a three-dimensional view of a vehicle, according to anillustrative embodiment of the invention.

FIG. 10 is a block diagram of a control system for dynamicallycontrolling the stability of a vehicle, according to an illustrativeembodiment of the invention.

FIG. 10A is a block diagram of position of the center of gravity of avehicle with respect to a ground-contacting element of the vehicle.

FIG. 10B is a block diagram of an alternative position of the center ofgravity of the vehicle of FIG. 10A with respect to a ground-contactingelement of the vehicle.

FIG. 11A is a schematic illustration of a vehicle, according to anillustrative embodiment of the invention.

FIG. 11B is a schematic illustration of a vehicle, according to anillustrative embodiment of the invention.

FIG. 11C is a schematic illustration of a vehicle, according to anillustrative embodiment of the invention.

FIG. 11D is a schematic illustration of a vehicle, according to anillustrative embodiment of the invention.

FIG. 12A is a schematic illustration of a vehicle, according to anillustrative embodiment of the invention.

FIG. 12B is a schematic illustration of a vehicle, according to anillustrative embodiment of the invention.

FIG. 12C is a schematic illustration of a vehicle, according to anillustrative embodiment of the invention.

FIG. 12D is a schematic illustration of a vehicle, according to anillustrative embodiment of the invention.

FIG. 13A is a three-dimensional view of a vehicle, in accordance with anembodiment of the invention.

FIG. 13B is an alternative configuration of the vehicle of FIG. 13A.

FIG. 14 is a schematic illustration of a vehicle, according to anillustrative embodiment of the invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

A balancing vehicle is shown in FIG. 3. The balancing vehicle includes aground-contacting module 32 which, in the embodiment that is shown, is apair of co-axial wheels powered by motors. A controller is coupled tothe motor for providing a control signal in response to changes in thecenter of gravity of an assembly that includes the vehicle along with arider. As the rider 10 mounts the vehicle, the controller module sensesthe change in the center of gravity 36 and controls power to the wheels32 based upon changes to the center of gravity 36 about a fore-aft plane42 using a control loop. As the center of gravity 36 moves forward inthe fore direction, power is provided to the wheels and the vehicle willmove forward. As the center of gravity moves in the aft direction inresponse to the movement of the rider, the vehicle will slow and reversedirection such that the vehicle moves in the aft direction. As a changein the center of gravity is sensed, torque is applied to one or more thewheels (or other ground-contacting members) of the vehicle by operationof the control loop and a wheel actuator (not shown).

The pitch of the vehicle may also be sensed and compensated for in thecontrol loop. The control module includes gyroscopes for sensing changesin the position of the center of gravity. The vehicle that is shownincludes a platform 12 for supporting the rider and a control stalk 14and 16. Appropriate force transducers may be provided to sense leftwardand rightward leaning and related controls provided to cause left andright turning as a result of the sensed leaning. The leaning may also bedetected using proximity sensors. Similarly, the vehicle of thisembodiment may be equipped with a foot- (or force-) actuated switchlocated on the platform 12 to activate the vehicle, in such a mannerthat the switch is closed so as to power the vehicle automatically whenthe subject contacts the platform 12. This embodiment further includes asupport 34, 38, 40 for the rider; the support may include a seat 34 onwhich the rider can rest.

In a first embodiment, the seat 34 is attached to the control stalk 16as shown in FIG. 3A. The rider 10 then uses his body and momentum tomove the center of gravity of the combination of the vehicle and therider in either a forward or in an aft direction. In another embodiment,the seat 34 is attached to the platform 12 via a pivot point 44 as shownin FIG. 3B. The pivot may be a simple pivot such that the pivot movesonly in the fore and aft directions or the pivot may be a universalpivot so that the seat may pivot in any direction. One example of auniversal pivot is a spring. Further, the pivot may be mounted to theplatform along the axis of the wheels, or the pivot may be mounted atother locations such as along the rear edge of the platform.

In yet another embodiment, a seat is attached to the platform using oneor more rails 46 on which the seat 34 slides as shown in FIG. 3C. Insuch an embodiment, the movement of the seat 34 by the rider causes achange in the position of the center of gravity of the vehicle and itsload. If the seat is moved in the fore direction sensors sense theresulting tilt of the vehicle and cause the vehicle to increase in speedin the fore direction. If the seat is slid in the aft direction, thevehicle 30 will slow down correspondingly. In certain embodiments of theinvention, a centering mechanism, such as, a spring may be incorporatedwith either the pivot or sliding seat, so the seat will return to aposition such that the vehicle is substantially stationary when a riderdisengages from the vehicle. In another embodiment, as shown in FIG. 3D,a seat 50 is mounted to the platform 12. The seat and the linkage 52 tothe platform do not include a pivot. The seat in this embodimentpreferably extends the length of the platform. When a rider engages thevehicle and sits on the seat, the rider may adjust the center of gravityby sliding her body along the length of the seat.

In a further embodiment, the vehicle includes a bar linkage mechanism,such as a four-bar linkage, that is attached to the control stalk asshown in FIG. 4A. The four-bar linkage mechanism is also attached to aseat by another bar (seat post) which is coupled to the four-bar linkageabout a common pivot point of the four-bar linkage or coupled to a barin the linkage. The four-bar linkage mechanism allows the seat to movein an arc which simulates a rocking motion similar to that of a rockingchair about the base platform as shown in FIG. 4C. FIG. 4B shows oneposition of the four-bar linkage 55 as would occur if a rider leanedbackwards shifting the center of gravity in the aft direction. The riderboth moves in the aft direction and also rotates in the aft directionand as such both, translation and rotation are coupled together. Viewedin another way, the four-bar linkage allows the seat to move in an arcabout a virtual pivot point. The virtual pivot point can be located at apoint above the seat. In other embodiments, the virtual pivot point maybe located below the seat. As the seat 34 both translates and rotatesthe center of gravity 35 moves in a straight line in the fore-aft planeas shown in FIG. 4D.

In other embodiments, the center of gravity need not move in a straightline and the position of the center of gravity may vary. The motion ofthe seat creates a rider experience that is different from the seatsdiscussed above in FIGS. 3A-3D. In this embodiment, there is no positionthat the seat automatically returns to. As such, there are no peaks orwells in terms of the amount of energy that is required to move thecenter of gravity. In this embodiment, no arm force is required tomaintain a position of the center of gravity relative to the wheel axisas is the case with simple and universal pivots as shown in FIGS. 3A-3C.This allows both ease of pitch control and the ability of the rider tofind the center of gravity position above the axle of the vehicle sothat the vehicle is substantially stationary. The virtual pivotmechanism allows the seated rider, to have a similar experience on thedynamically balancing vehicle that a standing rider would have.

In the version of the vehicle described with respect to FIGS. 4A-4E, thecontrol stalk is held by the rider by a pair of hand grips that extendfrom the control stalk. As a rider sits on the seat, the seat can moveabout the fore-aft plane and the seat will both shift and rotate whenthe rider moves, thus changing the center of gravity.

Although the embodiment, shown above has a linkage mechanism forproviding the coupling of rotation and translation, other structures andsystems could also be designed to provide this functionality such asthose shown in, but not limited to FIGS. 5A-E and FIGS. 6, 6A, 6B, and6C and the present invention are not intended to be limited tomechanical linkages.

In a further embodiment, the four-bar linkage includes non-rigid membersthat can flex. For example, FIG. 4E shows a support structure wheremembers B and C each flex and member D is rigid as are the couplings ofmembers B and C to platform A. In this embodiment members B and C areshown such that the two members lean inwards to meet member D. As forceis placed on the seat through member D by the rider in the fore-aftdirection, the members B and C will flex such that the seat will move ina rocking motion about a virtual pivot point that lies above the seat.The motion of members B and C is shown in FIG. 4E by the dotted lines.As such, member D which supports the seat will both translate androtate. Further, pivots may be included in such an embodiment, so thatthe linkage both pivots and flexes. For instance, pivots may be placedat the point where member D comes into contact with members B and C asshown in the figure. In still another variation, members B and C may bepositioned so rather than leaning inward, the two members are outwardleaning. In this type of embodiment, the seat will move much like arocking chair. If a rider leans in the fore direction the seat willtranslate in the fore direction and the seat will rotate such that thefore-most part of the seat will be lower than the aft-most part of theseat. This is different from the embodiment that is shown in FIG. 4Ewherein if a rider causes the seat to translate in the fore direction,the seat will rotate such that the fore-most part of the seat iselevated as compared to the aft-most part of the seat.

FIGS. 5A-5E each show different embodiments in which both translationand rotation are coupled. In FIG. 5A the seat 34 is attached to a bar 58via a pivot 60. The seat further includes a series of protrusions 62formed in an arc which mesh with a sprocket 64. The sprocket 64 isattached to the bar 58 and can spin about an axis 66. The bar includes asecond sprocket 67 which can rotate about a central axis 69. Thesprockets 64, 67 each reside on a strip/track 70 that includesprotrusions 72 that mesh with the sprockets 64, 67. As a user of thevehicle moves the seat in a fore or aft direction the seat willtranslate and rotate due to the protrusions 62 that are formed in an arcand which are coupled to the seat. In other embodiments, the track onwhich the seat slides may have a different profile. For example, thetrack may be convex, concave, or have a varying profile along itslength. If the track has a varying profile, the rider needs to applymore force to move the seat along certain portions of the track. Thus,different track profiles may be employed in order to shape the path ofthe center of gravity and the center of gravity need not move in astraight line.

In FIG. 5B the seat 34 attaches to a slider 75 about a pivot point 76.The slider fits on a rail 78 and the slider 75 can slide on the rail 78.Attached to the slider at the seat are at least two pulleys 79, 80. Thepulleys 79, 80 are positioned toward opposite ends of the seat about theslider. One or more wires or cables 81 are attached to the seat and afixed portion of the vehicle such as the rail. The cables 81 engage thepulleys 80, 79. As the seat is slid by the rider in the forward or aftdirection, the pulleys cause the seat to tilt due to changing tension inthe cables. The cables are coupled to either end of the rail 85, 86 orsome other component of the vehicle and also to the seat at oppositeends 83, 84. In the embodiment as shown, there are two separate cables,one of which runs from rail end 86 across pulley 79 and attaches to theseat at 84. The second cable attaches to the seat at 83 and acrosspulley 80 and attaches at the rail end 85. If the seat is moved in theaft direction, the edge of the seat in the aft direction will be rotatedand lowered. Similarly, if the seat is moved by the rider in the foredirection, the fore-most part of the seat will rotate and will belowered.

In FIG. 5C, the seat is coupled to a slider 87 about a pivot point 88.The slider 87 is seated on a rail 89 and provides for the seat to beslid in a fore and an aft direction. The seat also includes twoextensions 34A, 34B that each have two wheels 90 mounted thereto.Between each pair of wheels is a straight track which includes an arc89A, 89B at each end of the track. As the seat is slid in either thefore or the aft direction the wheels roll along the arc and cause theseat to tilt about the pivot point. It can be imagined that the trackhas a varying curvature, such that the center portion of the track isitself curved and that the ends have a greater radius of curvature ascompared to the center.

In FIG. 5D, the seat 34 rides on a track 200. The seat 34 is coupled toa transmission 210 by a pivot 220. The transmission is coupled to a pairof friction wheels 225, 230. In this embodiment, translation of the seat34 is directly coupled to rotation of the seat. As the seat is moved bythe rider and the friction wheels rotate along the track the seat willalso rotate. In the embodiment that is shown, the wheels rotate agreater amount than the pivot rotates the seat. The transmissiontherefore, causes the seat to pivot/rotate at a fraction of the rotationof the friction wheels. It should be understood that all of the tracksthat are shown in FIGS. 5A-5D may be the same length as the platform ormay extend beyond the length of the platform in the fore-aft directionor may be shorter than the length of the platform. The support structurealso will include a mechanism for holding the track at a proper seatheight. For example, the track may be mounted to the control stalk, ormay sit on its own mounting structure that is coupled to the platform.For example, the mounting structure may be a shaft.

FIG. 6 shows a side view of an embodiment of the dynamically balancingvehicle with a detachable rocker seat. The rocker seat includes asupport structure 95. The bottom portion of the support structurecontacts the platform and is shaped like an arc 97 allowing the seat 34to rock. The arc shaped lower member 97 of the support structure 95 iscoupled to the platform 12 via a moving contact point. The arc shapedmember 97 member rotates equally in the fore and aft plane in thisembodiment. Although in other embodiments, rotation may be limited ineither the fore or aft direction. The support structure may also becoupled to the platform via a pair of rails. In this embodiment, thesupport structure rests on the rails that the rails include a mechanismthat constrains the support structure from moving in any other planeother than the fore-aft plane. In such an embodiment, the arch shapedlower portion of the support structure is not coupled to the platform ata contact point. In such an embodiment, the arc shaped member may rollon a series of rails or wheels. In another embodiment, the supportstructure may include a guide pin that extends through the supportstructure and is enclosed by the rails on either side of the supportstructure. In such an embodiment, the seat can rock in the fore-aftdirection about a virtual pivot that is above the seat. It should beunderstood that a virtual pivot point need not be above the seat, incertain embodiments, the virtual pivot point may exist below the seat,for example.

It should be recognized, that the lower surface of the support structurethat is formed in an arc may have any number of radii. For example, thelower surface may have a greater curvature at the edges and less of acurvature at its center, so that as the support structure rocks aboutits central portion, each unit of translation there is proportional to adegree of rotation, but as the support structure is rocked furthertoward the edges, there is a greater degree of rotation for each unit oftranslation.

In another version, the lower surface of the support structure 150includes two pins 160, 165 at the edges of the arc as shown in FIG. 5E.As the support structure rocks 170 to the edge, one of the pins 160 or165 will engage with a recess 160A or 165A in the platform 12. If therider continues to lean in the same direction, the support structurewill rotate about the pin 160 or 165. Thus, there are two differentratios of translation to rotation for this embodiment. As the supportstructure 170 rocks about the arc there is less rotation for each unitof translation as compared to motion about the pin 160 or 165 in whichthere is rotation without translation when the pin engages with therecess of the platform.

The embodiment of FIG. 6, in which the support structure has an arc asthe lower surface, may be coupled to the platform in any one of a numberof ways. For example, gravity may hold the support structure on theplatform 12. Further, the platform surface and the bottom surface of thesupport structure may be formed from materials having a high coefficientof friction. In another embodiment, as shown in FIG. 6A, the supportstructure 300 may be attached to the platform 12 via a simple cable 310under tension (including a spring 310A). In this embodiment, as thesupport structure rocks about the arc of the bottom surface 300A, thespring 310A stretches, and thus there is a restoring force returning thesupport structure 300 to a centered position as shown. As shown in FIG.6B, the support structure 400 may include a series of teeth 410 on thebottom arced surface 400A and the platform 12 may include a series ofmating teeth 420 for the bottom surface. As the support structure rocksthe teeth of the bottom surface and of the platform interlock.

In FIG. 6C, the support structure 500 is coupled to the platform 12about a pivot point 510. The pivot 510 is coupled to a member 520 whichextends down through the platform and which in this embodiment, rides ona pair of wheels 530. In this embodiment, the member 520 is rigid. Asforce is applied to the support structure 500 by the rider in thefore-aft directions, the support structure 500 will translate and thewheels 530 will rotate on the bottom side of the platform as shown. Thesupport structure 500 will also rotate about the pivot point 510 due tothe arched bottom side of the support structure 500A. In thisembodiment, the support structure 500 will maintain contact with theplatform at all times, including over rough terrain. Again, it should berecognized, that other mechanisms for coupling the support structure tothe platform can be envisioned and the present invention should not belimited by the embodiments that are shown.

In one embodiment, the platform of the vehicle includes one or morepressure sensors to sense the rider either engaging or disengaging fromthe vehicle. When the rider powers-up the vehicle and engages thevehicle, the vehicle enters a balancing mode. A control loop is madeoperational that senses changes to the position of the center of gravityand that causes the vehicle to move with respect to the changes. If thevehicle includes a seat, the rider may not engage the pressure sensorsbecause her feet may not make contact with the platform or the rider mayremove her feet from the platform. In order to overcome this problem,sensors, such as pressure sensors, may be included in the seat. Inanother embodiment, a mechanical device such as a link or tube may beemployed to make contact with the platform when the rider engages thevehicle.

The support structure may be designed to either fold or compress inorder to allow for the rider to better engage/disengage with the vehicleand also for shock absorption. For example FIGS. 7A-C shows a foldingseat which may be employed with the previously described vehicles. InFIG. 7A the seat is in full view and is positioned as if a rider issitting on the seat. The sides of the seat expand in an outwarddirection like an accordion when weight is put on the seat. FIG. 7Bshows a rider sitting on the seat. FIG. 7C shows the position of theseat when a rider 10 engages/disengages with the vehicle. If the rideris already on the vehicle, the seat 34 rises up and folds as the riderstands and the support structure 92 contracts inwardly reducing the sizeof the support.

The support structure for the seat may also include a mechanism forallowing lateral movement in a plane substantially perpendicular to thefore-aft plane of the vehicle. The vehicle may include sensors to sensethe lateral movement. The sensors can be tied into a control loop sothat if a rider leans to the right more power is applied to the leftwheel allowing the vehicle to turn to the right. In other embodiments ofthe support structure, lateral movement may not be tied to sensors and acontrol loop, but may simply perform the function of allowing the riderto readily shift his or her weight of over rough terrain.

The support structure may also include knee rests 290 as shown in FIG.7D to allow more consistent rider coupling to the vehicle and to providepostural advantage and/or partial body support.

FIG. 8 shows another embodiment, in which the seat 34 both translatesand rotates. It is preferable that translation and rotation are coupled.In this embodiment, there are force sensors 120 in the seat. As a ridershifts his weight on the seat 34, the force sensors 120 sense thechange. Based upon the changes in force, both a linear actuator 125 anda rotational actuator 130 are engaged. If the rider shifts his weightsuch that more weight is provided to force sensor A than to B, thelinear actuator 125 will cause translation of the seat in the foredirection. Additionally, the seat will be rotated in the fore directionby the rotational actuator 130, such that the fore-most part of the seatwill be lowered and the aft-most part of the seat will be raised. Theembodiment as shown also includes a linear actuator 135 that provideslinear motion in the vertical direction. This actuator 135 makesengagement and disengagement with the vehicle easier. In thisembodiment, both translation and rotation are controlled by mechanicalactuators. Using mechanical actuators for providing translation androtation of the seat, assists individuals having a reduced strengthcapacity when compared to the simpler mechanical designs that requirethe rider to manually shift the position of the seat, to significantlyshift their weight using their own strength, and to maintain a positionof either leaning in the fore or in the aft direction using their musclestrength.

FIG. 9 is a three-dimensional view of a vehicle 1100, according to anillustrative embodiment of the present invention. A human subject (notshown) rests on a support 1102 in an enclosure 1104 that at leastpartially encloses the human subject. The vehicle 1100 includes at leasttwo ground-contacting elements 1108, 1110. The two ground-contactingelements 1108, 1110 are coupled to a platform 1106. Theground-contacting element 1108 is laterally disposed to theground-contacting element 1110. The ground-contacting elements eachrotate about an axle 1114 and are powered by at least one drive 1116(e.g., a motorized drive). A controller (1160) is coupled to the drive1116 for providing a control signal in response to changes in vehicleorientation (e.g., pitch) and position of the center of gravity 1112 ofthe vehicle 1100.

The ground-contacting elements 1108 and 1110 are wheels in thisembodiment of the invention. As the term is used herein,ground-contacting elements (e.g., ground-contacting elements 1108 and1110) can be wheels or any other structure that supports the vehiclewith respect to an underlying surface and controls the locomotion and/orbalancing of the vehicle. In some embodiments, one or moreground-contacting elements of a vehicle are a track, roller, ball,arcuate element or leg.

As the human subject mounts the vehicle 1100, the controller 1160implements a control loop and senses a change in the vehicle's 1100orientation that can result from a change in the position of the centerof gravity 1112 in a fore-aft plane and controls power provided to theground-contacting elements 1108, 1110 based upon the change to theposition of the center of gravity 1112. In response to the change in thevehicle's 1110 orientation and changes in the position of the center ofgravity 1112, torque is applied to the ground-contacting elements 1108,1110 to dynamically stabilize the vehicle 1100.

In one embodiment, as the position of the center of gravity 1112 movesin a fore direction (toward the negative X-Axis direction), the drive1116 provides power to the two ground-contacting elements 1108, 1110sufficient to cause the vehicle 1100 to move forward (toward thenegative X-Axis direction). As the center of gravity 1112 moves in theaft direction (toward the positive X-Axis direction), the drive 1116provides power to the two ground-contacting elements 1108, 1110sufficient to cause the vehicle 1100 to slow and reverse direction suchthat the vehicle 1100 moves backward (toward the positive X-Axisdirection). In some embodiments, as the position of the center ofgravity 1112 moves laterally, (along the positive or negative Z-axis),the drive component 1116 provides power to the two ground-contactingelements 1108, 1110 sufficient to cause the vehicle 1100 to turn left orright. More power can be applied to the left ground-contacting elementto turn right. In some embodiments, less power is provided to the rightground-contacting element to turn right. In some embodiments, more poweris provided to the left ground-contacting element and less power isprovided to the right ground-contacting element to turn right.

The pitch of the vehicle 1100 (angular orientation of the vehicle 1100about the axle 1114 of the vehicle 1100) may also be sensed andcompensated for in the control loop. The controller includes gyroscopesfor sensing orientation of the vehicle 1100 that can result from changesin the position of the center of gravity 1112. Appropriate forcetransducers may be provided to sense leftward and rightward leaning andrelated controls provided to cause left and right turning as a result ofthe sensed leaning. The leaning may also be detected using proximitysensors. Similarly, the vehicle of this embodiment may be equipped witha foot- (or force-) actuated switch located on, for example, theplatform 1106 or support 1102 to activate the vehicle 1100, in such amanner that the switch is closed so as to power the vehicle 1100automatically when the subject contacts the platform 1106.

In another embodiment, as the center of gravity 1112 moves in the foredirection (toward the negative X-Axis direction), the drive 1116provides power to the two ground-contacting elements 1108, 1110sufficient to cause the vehicle 1100 to move backward (toward thepositive X-Axis direction). As the center of gravity 1112 moves in theaft direction (toward the positive X-Axis direction), the drive 1116provides power to the two ground-contacting elements 1108, 1110sufficient to cause the vehicle 1100 to slow down and reverse directionsuch that the vehicle 1100 moves forward (toward the negative X-Axisdirection).

Vehicle 1100 pitch variation is decreased during operation when thevehicle 1100 is dynamically stabilized based on the change in theposition of the center of gravity 1112 rather than in response to achange in pitch. It also shortens the time it takes the vehicle 1100 torespond to an acceleration and/or deceleration command. The vehicle 1100accelerates and/or decelerates by restoring the position of the centerof gravity 1112 of the vehicle 1100 over the location that theground-contacting elements 1108 and 1110 contact the ground. If thevehicle 1100 was accelerated and/or decelerated in response to a changein pitch, a controller of the vehicle 1100 would first need to induce achange in the position of the center of gravity 1112 relative to asteady state position and then command the drive 1116 to operate theground-contacting elements 1108 and 1110 in such a manner as to positionthe center of gravity 1112 above the location where theground-contacting elements contact the ground. The time required toinduce a change in the position of the center of gravity 1112 back tothe steady state position is a time delay for the vehicle 1100 torespond to an acceleration and/or deceleration command compared toacceleration and/or deceleration in response to a change in the positionof the center of gravity. The vehicle 1100 does not need to induce thechange in the position of the center of gravity 1112 from a steady statebecause the change of the position of the center of gravity 1112 isinherit in the acceleration and/or deceleration command. Theacceleration and/or deceleration command necessitates a change in theorientation of the vehicle 1100 to position the center of gravity 1112in the correct position so that acceleration and/or deceleration canbegin.

FIG. 10 is a block diagram of a control system 1200 for dynamicallycontrolling the stability of a vehicle (e.g., vehicle 1100 as discussedabove in FIG. 9), according to an illustrative embodiment of theinvention. A controller 1202 receives an input characteristic of aposition of a center of gravity of a vehicle (e.g., center of gravity1112 as discussed above in FIG. 9) from a sensor module 1204. Based onat least the position of the center of gravity provided by the sensormodule 1204, the controller 1202 commands torque T of at least one ofthe left motorized drive 1206 or right motorized drive 1208 (e.g.,torque applied to the corresponding ground contact elements).

FIGS. 10A and 10B are block diagrams that illustrate the effect of theposition of the center of gravity 1222 of a vehicle 1230 on operation ofthe vehicle 1230, according to an illustrative embodiment of theinvention. The vehicle 1230 has a total mass M₂ (weight of M₂g). Themass of a payload and a portion of the vehicle 1230 is denoted as M₁(weight of M₁g) which corresponds to the mass of the center of gravity1222. The mass of two laterally disposed contacting elements 1220 isdenoted as mass M₀ (weight of M₀g). The weight of the vehicle 1230 isexpressed as:

M ₂ g=M ₁ g+M ₀ g  EQN. 1

The portion of the vehicle 1230 capable of moving along the X-Axisdirection relative to the position of the ground-contacting elements1220 is represented by the center of gravity 1222. Referring to FIG.10A, the center of gravity 1222 is located at an initial location 1234above the location 1238 where the ground-contacting elements 1220contact the ground.

Referring to FIG. 10B, the center of gravity 1222 is located at alocation 1242, at a distance L along the negative X-Axis directionrelative to the initial location 1234. In one embodiment, the center ofgravity 1222 is positioned at location 1242 by a human subject movingthe position of the center of gravity of the vehicle 1230 (e.g.,similarly as described herein with respect to, for example, FIG. 9). Thesensor module 1204 (of FIG. 10) provides the pitch of the vehicle 1230and the orientation of the vehicle 1230, that change as the position1242 of the center of gravity 1222 changes, to the controller 1202. Thecontroller 1202 outputs a signal to the left motorized drive 1206 andright motorized drive 1208 to apply a torque [T=(M₁g)(L)] to theground-contacting elements 1220 to cause the ground-contacting elements1220 to move in the direction (e.g., forward along the negative X-Axisdirection) the center of gravity 1222 has been displaced from theprevious location 1238 to maintain balance of the vehicle 1230.

The masses of the vehicle 1230 can be advantageously distributed betweenthe payload and related structure (collectively 1222) and the groundcontacting-elements and related structure (collectively 1220) tomaximize acceleration and deceleration performance. In one embodiment,it is advantageous to locate a larger percentage of the total vehicle1230 mass with the moving portion of the vehicle 1230 (i.e., with thepayload and related structure 1222) to maximize acceleration anddeceleration performance. Placing more of the total vehicle 1230 masswith the moving portion 1222 enables the larger amount of mass tocontribute to generating the motor commands required to accelerate ordecelerate the vehicle 1230. If, however, more of the total vehicle 1230mass was placed with the ground-contacting elements and relatedstructure 1220, the larger percentage of mass would be a load that thevehicle 1230 needs to move as part of the entire vehicle 1230.

[

The controller 1202 also interfaces with a user interface 1210 and awheel rotation sensor 1212. The user interface 1210 can, for example,include controls for turning the vehicle on or off, or for triggeringdifferent operating modes of the vehicle (e.g., the operating modesdescribed with respect to FIGS. 13A and 13B).

The sensor module 1204 detects one or more vehicle parameters todetermine a change in the position of the center of gravity of thevehicle. In one embodiment, the sensor module 1204 generates a signalindicative of a change in the position of the center of gravity at oneinstance in time with respect to the position of the center of gravityat another instance in time. For example, a distance sensor attached toa spring, a load sensor, an inclinometer, a gyroscope, whiskers and/oran angular rate sensor can be used to determine a change in the centerof gravity of the vehicle. Other sensors (e.g., optical sensors and/ormagnetic sensors) can also be employed and are therefore within thescope of the present invention.

The controller 1202 includes a control algorithm to determine the amountof torque to be applied by the left motorized drive 1206 and/or rightmotorized drive 1210 based on the position of the center of gravity. Thecontrol algorithm can be configured, for example, during the design ofthe vehicle or in real time, on the basis of a current operating mode ofthe vehicle, operating conditions experience by the vehicle, as well aspreferences of a human subject. The controller 1202 can implement thecontrol algorithm for example, by using a control loop. The operation ofcontrol loops is well known in the art of electromechanical engineeringand is outlined, for example, in Fraser & Milne, Electro-MechanicalEngineering, IEEE Press (1994), particularly in Chapter 11, “Principlesof Continuous Control” which is incorporated herein by reference.

As an example, not meant to be limiting, the control algorithm can takethe form:

Torque Command=K·(C+O)  (EQN. 2)

where K is the gain, C is a vector defining the position of the centerof gravity of the vehicle, and O is an offset. The position of thecenter of gravity, C, can be in the form of an error term defined as thedesired position of the center of gravity minus the sensed position ofthe center of gravity. The desired position of the center of gravity canbe for example, a predetermined constant in the control algorithm.Alternatively, a human subject in the vehicle can set the position ofthe center of gravity via a user interface. In this embodiment, uponstarting the vehicle and prior to allowing movement of the vehicle, ahuman subject can activate a switch on the vehicle that triggersdetermination of the desired position of the center of gravity based oninputs received from the sensor module. This allows the human subject toacquire a known initial position of the center of gravity, from whichthe human subject can then deviate so as to cause a change in theposition of the center of gravity.

The gain, K, can be a predetermined constant, or can be entered oradjusted by the human subject through the user interface 1210. Gain Kis, most generally, a vector, with the torque determined as a scalarproduct of the gain and the position of the center of gravitydisplacement vector. Responsiveness of the vehicle to changes in theposition of the center of gravity can be governed by K. For example,increasing the magnitude of at least one element of vector K causes ahuman subject to perceive a stiffer response in that a small change inthe position of the center of gravity results in a large torque command.

Offset, O, can be incorporated into the control algorithm to govern thetorque applied to the left motorized drive 1206 and right motorizeddrives 1208, either in addition to, or separate from, the direct effectof C. Thus, for example, the human subject can provide an input by meansof the user interface 1210, the input is treated by the controller 1202equivalently to a change, for example, in the position of the center ofgravity.

In one embodiment, steering can be accomplished by calculating thetorque desired for the left motorized drive 1206 and the torque desiredfor the right motorized drive 1208 separately. Additionally, trackingboth left wheel motion and the right wheel motion permits adjustments tobe made, as known to persons of ordinary skill in the control arts, toprevent unwanted turning of the vehicle and to account for performancevariations between the left motorized drive 1206 and the right motorizeddrive 1208.

In some embodiments, a change in the position of the center of gravityis sensed in the fore-aft plane and/or the lateral plane. Sensing achange in the position of the center of gravity in the lateral planeensures stability with respect to tipping in the lateral plane. In suchembodiments, lateral changes in the position of the center of gravityare used to trigger anti-tipping mechanisms or otherwise modify theoperation of the vehicles performance (e.g., altering the torque appliedto one or more ground-contacting elements). In some embodiments, lateralchanges in the position of the center of gravity are used to command thevehicle to turn left or right.

Steering may be accomplished in an embodiment having at least twolaterally disposed ground-contacting elements (e.g., a left and rightwheel), by providing, for example, separate motors for left and rightground-contacting elements. Torque desired for the left motor and thetorque desired from the right motor can be calculated separately.Additionally, tracking both the left ground-contacting element motionand the right ground-contacting element motion with theground-contacting element rotation sensors 1212 permits adjustments tobe made, as known to persons of ordinary skill in the control arts, toprevent unwanted turning of the vehicle and to account for performancevariations between the two motors. In some embodiments, steeringsensitivity is adjusted to a higher sensitivity when a vehicle is atlower speeds and lower sensitivity when a vehicle is at higher speeds toallow, for example, easier steering at higher speeds.

In some embodiments, the control system 1200 limits the speed of avehicle (e.g., vehicle 100 as discussed above in FIG. 9). The speedlimit can be set based on, for example, a maximum speed associated withthe operating mode of the vehicle (for example, as discussed below inconnection with FIG. 13A and FIG. 13B) or an input from the humansubject.

In one embodiment, the control system 1200 includes a speed limitingalgorithm that regulates the speed of the vehicle by controlling thepitch of the vehicle. The controller 1202 changes the pitch of thevehicle which moves the position of the center of gravity. Changes inthe position of the center of gravity causes the vehicle to accelerateor decelerate depending on which direction the center of gravity ismoved. The speed limiting algorithm causes the controller 1202 toaccelerate or decelerate the vehicle by adjusting a desired pitch angleΘ_(D). The pitch control loop of the system 1200 controls the system1200 to achieve the desired pitch angle Θ_(D).

The adjustment of the desired pitch angle θ_(D) is determined based onthe following relationship:

$\begin{matrix}{\Theta_{D} = {K\; 1*\left\lbrack {\overset{\overset{A}{}}{K\; 2*\left( {V_{SpeedLimit} - V_{cm}} \right)} + \overset{\overset{B}{}}{K\; 3*({IntegratedSpeedError})} + \overset{\overset{C}{}}{K\; 4*({Acceleration})}} \right\rbrack}} & \left( {{EQN}.\mspace{14mu} 3} \right)\end{matrix}$

where V_(SpeedLimit) is the current maximum speed of the vehicle, V_(cm)is the speed of the vehicle, K2 is a gain proportional to the differencebetween the vehicle's speed limit and the vehicle's actual speed, K3 isa gain on the Integrated Speed Error, which is the integrated differencebetween the vehicle's speed limit and the vehicle's actual speed, K4 isa gain on the acceleration of the vehicle, K1 is a gain on the overallcalculated desired pitch that can be a function of, for example, aposition of the center of gravity of the vehicle, and θ_(D) is thedesired pitch angle. The cumulative effect of terms A, B and C in EQN. 3is to cause the vehicle to pitch backward into a decelerationorientation if the speed limit is exceeded. The value of the desiredpitch angle, θ_(D) is varied in the control system 1200 to control thespeed of the vehicle.

In one embodiment, the desired pitch angle θ_(D) remains constant (e.g.,the vehicle remains level with respect to the ground plane). When apredefined maximum speed limit is reached, the control system 1200responds by setting the desired pitch angle θ_(D) to a value todecelerate the vehicle to prevent the vehicle from exceeding the maximumspeed limit. This has the effect of the control system 1200 commandingthe vehicle to pitch backwards which causes the speed of the vehicle todecrease.

In some embodiments, the control system 1200 is configured to accountfor the human subject commanding the vehicle to slow down. When thecontrol system 1200 determines that the human subject has caused theposition of the center of gravity to shift rearward, the controllerreduces the value of the gain K1. By reducing the value of the gain K1,the pitch angle terms in the control system 1200 (governed by, forexample, EQN. 3) are de-emphasized. Because the control system 1200de-emphasizes the pitch angle terms, the control system 1200 does notcommand the vehicle to pitch backwards as much as it would in theabsence of the human subject commanding the vehicle to slow down. Insome embodiments, the human subject and support return to a more levelorientation with respect to the ground as the vehicle speed decreases.

FIG. 11A is a schematic illustration of a vehicle 1300, according to anillustrative embodiment of the invention. The vehicle 1300 includes anenclosure 1302 coupled to a support 1304. The vehicle 1300 also includesat least one ground-contacting element 1310 coupled to a platform 1312.The ground-contacting element 1310 rotates about an axle 1314 which iscoupled to the platform 1312. In some embodiments, the ground-contactingelement 1310 is a wheel. In some embodiments, the vehicle 1300 includestwo or more laterally disposed ground-contacting elements 1310 whichassist with providing lateral stability to the vehicle 1300. In someembodiments, the ground-contacting element 1310 is a cluster of wheelsor arcuate elements that are disposed around the axle 1314. The clusterof wheels or arcuate elements rotate around the axle 1314 when providinglateral stability to the vehicle 1300.

A structure (combination of rail 1316 and rail guide 1318) couples theenclosure 1302 and support 1304 to the platform 1312 andground-contacting element 1310. The enclosure 1302 and support 1304 arecoupled to the rail 1316. The enclosure 1302, support 1304 and rail 1316slide relative to the rail guide 1318 that is coupled to the platform1312 of the ground-contacting element 1310. In this embodiment, a humansubject (not shown) manipulates an input device 1306 to cause a positionof a center of gravity 1340 of the vehicle 1300 to change. The inputdevice 1306 is coupled to a linkage 1308. The linkage 1308 is coupled tothe support 1304. The input device 1306 can be, for example, a controlstick, yoke, steering wheel or handlebar.

The human subject pushes the input device 1306 forward (toward thenegative X-Axis direction) which moves the enclosure 1302 and support1304 forward (toward the negative X-Axis direction) relative to theground-contacting element 1310. The position of the center of gravity1340 of the vehicle 1300 moves forward in response to the enclosure 1302and support 1304 moving forward. A forward torque is generated by theground-contacting element 1310 in response to the center of gravity 1340of the vehicle 1300 moving forward. The human subject pulls the inputdevice 1306 backward (toward the human subject's body and along thepositive X-Axis direction) which moves the enclosure 1302 and support1304 backward (toward the positive X-Axis direction) relative to theground-contacting element 1310. The position of the center of gravity1340 of the vehicle 1300 moves backward in response to the enclosure1302 and support 1304 moving backward. A negative torque is generated bythe ground-contacting element 1310 in response to the position of thecenter of gravity 1340 of the vehicle 1300 moving backward. In oneembodiment, the vehicle 1300 does not have a platform 1312 and the railguide 1316 is coupled to a structure attached to the at least oneground-contacting element 1310 (e.g., a cross bar coupling two laterallydisposed ground-contacting elements.

In some embodiments, when the enclosure 1302, support 1304 and rail 1316slide forward or backward relative to the rail guide 1318, platform 1312and ground-contacting element 1310, the enclosure 1302, support 1304 andrail 1316 remain level (or substantially level) relative to the ground.In alternative embodiments, when the enclosure 1302, support 1304 andrail 1316 slide forward or backward relative to the rail guide 1318,platform 1312 and ground-contacting element 1310, the enclosure 1302,support 1304 and rail 1316 pitch relative to the ground. The vehicle1300 can be adapted such that enclosure 1302, support 1304 and rail 1316pitch forward when the enclosure 1302, support 1304 and rail 1316 slideforward, or alternatively, adapted such that enclosure 1302, support1304 and rail 1316 pitch backward when the enclosure 1302, support 1304and rail 1316 slide forward.

In some embodiments, the human subject shifts his/her weight forward orbackward to move the position of the center of gravity to cause thevehicle to move forward or backward, respectively, without causing theenclosure 1302, support 1304 and rail 1316 to move relative to the railguide 1318, platform 1312 and the ground-contacting elements 1310.

In some embodiments, the linkage 1308 is coupled to a device thatprovides stiffness or damping to movement of the linkage 1308 to, forexample, enforce particular types of inputs to the vehicle and/orenhance the human subject's experience. In some embodiments, the devicelimits the speed that the linkage 1308 is permitted to move which limitsthe speed at which the position of the center of gravity 1340 ispermitted to change and, therefore, limits the rate of change of thespeed of the vehicle 1300.

In some embodiments, the device damps oscillations in the movement ofthe linkage 1308 to reduce oscillations in the pitch control loop and/orcenter of gravity control loop of a controller that controls operationof the vehicle 1300. In the absence of the device, oscillations inducedin the linkage 1308 by, for example, a human subject pushing or pullingthe input device 1306 would result in oscillations in the pitch and/orspeed of the vehicle 1300.

In some embodiments, the rail 1316 and/or rail guide 1318 includes adamper to prevent the speed of the vehicle 1300 from oscillating whenthe rail 1316 moves out of phase with respect to the rail guide 1318 dueto, for example, an external disturbance or on-vehicle disturbance. Forexample, when the vehicle 1300 travels over a bump, the rail 1316 maymove relative to the rail guide 1318, thereby moving the position of thecenter of gravity 1340 of the vehicle 1300. Movement of the position ofthe center of gravity 1340 causes the vehicle 1300 to accelerate ordecelerate. Therefore, a damper coupling the rail 1316 to the rail guide1318 would reduce the high frequency motion otherwise induced by thebump, and reduce the variation in the speed of the vehicle 1300 due tothe bump. The damper would not damp lower frequency motions introduced,for example, by a human subject pushing the input device 1306 to commanda change to the position of the center of gravity 1340 of the vehicle.In some embodiments, the damper is configured to damp high frequencyoscillations or impulses. The damper can be a mechanical damper couplingthe rail 1316 to the rail guide 1318. In some embodiments, the damper isa damping term implemented in a controller (e.g., controller 1202 asdiscussed above).

In some embodiments, the vehicle 1300 includes an additional mechanismthat allows for changing the position of the center of gravity 1340 inplanes other than the fore-aft plane. In one embodiment, the vehicle1300 includes a second rail/rail guide pair that allows for changing theposition of the center of gravity 1340 in the lateral direction (i.e.,along the Z-Axis direction).

In an alternative embodiment, the vehicle 1300 includes a foot membercoupled to the platform 1312. When the human subject pushes against thefoot member, the support 1304 and enclosure 1302 move backward (alongthe positive X-Axis direction) relative to the ground-contacting element1310. The center of gravity 1340 of the vehicle 1300 moves backward inresponse to the enclosure 1302 and support 1304 moving backward. Anegative torque is generated by the ground-contacting element 1310 inresponse to the center of gravity 1340 of the vehicle 1300 movingbackward.

FIG. 11B is a schematic illustration of the vehicle 1300, according toan illustrative embodiment of the invention. The enclosure 1302 iscoupled to the support 1304. The at least one ground-contacting element1310 is coupled to the platform 1312. The ground-contacting element 1310rotates about the axle 1314. In this embodiment, a structure (the pivotmember 1320) couples the support 1302 and enclosure 1304 to the platform1312 and ground-contacting element 1310. The enclosure 1302 and support1304 are coupled to a pivot member 1320 with a pivot mechanism 1322located at a first end 1348 of the pivot member 1320. The pivot member1320 is coupled to the platform 1312 at a second end 1344 of the pivotmember 1320. The enclosure 1302 and support 1304 pivot about the pivotmechanism 1322.

In this embodiment, a human subject (not shown) sits on the support 1304and manipulates an input device 1306 to cause a position of a center ofgravity 1340 of the vehicle 1300 to change. The input device 1306 iscoupled to the linkage 1308. The linkage 1308 is coupled to the support1304. The human subject pushes the input device 1306 forward (toward thenegative X-Axis direction) which causes the enclosure 1302 and support1304 to pivot about the pivot mechanism 1322 (around the Z-Axis), movingthe enclosure 1302 and support 1304 forward (toward the negative X-Axisdirection) relative to the ground-contacting element 1310. The positionof the center of gravity 1340 of the vehicle 1300 moves forward inresponse to the enclosure 1302 and support 1304 moving forward. Aforward torque is generated by the ground-contacting element 1310 inresponse to the position of the center of gravity 1340 of the vehicle1300 moving forward.

The human subject pulls the input device 1306 backward (toward the humansubject's body and along the positive X-Axis direction) which causes theenclosure 1302 and support 1304 to pivot about the pivot mechanism 1322,moving the enclosure 1302 and support 1304 backward (toward the positiveX-Axis direction) relative to the ground-contacting element 1310. Theposition of the center of gravity 1340 of the vehicle 1300 movesbackward in response to the enclosure 1302 and support 1304 movingbackward. A negative torque is generated by the ground-contactingelement 1310 in response to the position of the center of gravity of thevehicle 1300 moving backward.

In some embodiments, the pivot mechanism 1322 permits motion of theenclosure 1302 and support 1304 in two or more degrees of freedom. Theenclosure 1302 and support 1304 also pivot about the X-Axis. Theenclosure 1302 and support 1304 rotate about both the Z-Axis (change inpitch) and the X-Axis (change in roll angle). In some embodiments, thechange in roll angle causes the vehicle 1300 to turn left or right. Insome embodiments, the position of the center of gravity 1340 moves inthree degrees of freedom (i.e., along the X-Axis, Y-Axis and Z-Axis).

FIG. 11C is a schematic illustration of the vehicle 1300, according toan illustrative embodiment of the invention. The enclosure 1302 iscoupled to the support 1304. The at least one ground-contacting element1310 is coupled to the platform 1312. The ground-contacting element 1310rotates about the axle 1314. The enclosure 1302 and support 1304 arecoupled to at least one four-bar linkage 1324 (first bar 1324 a andsecond bar 1324 b). A first end 1352 a of the first bar 1324 a iscoupled to the support 1304. A second end 1356 a of the first bar 1324 ais coupled to the platform 1312. A first end 1352 b of the second bar1324 b is coupled to the support 1304. A second end 1356 b of the secondbar 1324 b is coupled to the platform 1312.

The enclosure 1302 and support 1304 move along a path 1360 defined by arotation of the four-bar linkage 1324 about the axle 1314 of theground-contacting element 1310 in the X-Y plane. In this embodiment, ahuman subject (not shown) manipulates an input device 1306 to cause theposition of the center of gravity 1340 of the vehicle 1300 to change.The input device 1306 is coupled to the linkage 1308. The linkage 1308is coupled to the support 1304. The human subject pushes the inputdevice 1306 forward (toward the negative X-Axis direction) which movesthe enclosure 1302 and support 1304 along the path 1360 defined by therotation of the four-bar linkage 1324, moving the enclosure 1302 andsupport 1304 forward (toward the negative X-Axis direction) relative tothe ground-contacting element 1310. The position of the center ofgravity 1340 of the vehicle 1300 moves forward in response to theenclosure 1302 and support 1304 moving forward. A forward torque isgenerated by the ground-contacting element 1310 in response to theposition of the center of gravity 1340 of the vehicle 1300 movingforward.

The human subject pulls the input device 1306 backward (toward the humansubject's body and along the positive X-Axis direction) which moves theenclosure 1302 and support 1304 along the path 1360 defined by therotation of the four-bar linkage 1324, moving the enclosure 1302 andsupport 1304 backward (toward the positive X-Axis direction) relative tothe ground-contacting element 1310. The position of the center ofgravity 1340 of the vehicle 1300 moves backward in response to theenclosure 1302 and support 1304 moving backward. A negative torque isgenerated by the ground-contacting element 1310 in response to theposition of the center of gravity 1340 of the vehicle 1300 movingbackward.

In some embodiments, the vehicle 1300 includes two laterally disposedground-contacting elements. The vehicle also includes two four-barlinkages (e.g., two of the four-bar linkages 1324). Each four-barlinkage is coupled to one of the two laterally disposedground-contacting elements, similarly as described with respect to FIG.11C.

In some embodiments, one or more four-bar linkages are flexible bars.The flexible bars bend to permit, for example, the enclosure and supportto move along a path (e.g., the path 1360 of FIG. 11C).

FIG. 11D is a schematic illustration of the vehicle 1300, according toan illustrative embodiment of the invention. The enclosure 1302 iscoupled to the support 1304. The at least one ground-contacting element1310 is coupled to the platform 1312. The ground-contacting element 1310rotates about the axle 1314. A structure (combination of rail 1316 andrail guide 1318) couples the enclosure 1302 and support 1304 are coupledto the platform 1312 and ground-contacting element 1310. The enclosure1302 and support 1304 are coupled to the rail 1316. The rail guide 1318is coupled to the platform 1312 of the ground-contacting element 1310.The enclosure 1302, support 1304 and rail 1316 slide together relativeto the rail guide 1318.

In this embodiment, a human subject (not shown) manipulates an inputdevice 1306 to cause the position of the center of gravity 1340 of thevehicle 1300 to change. This embodiment lacks a linkage (e.g., thelinkage 1308 of FIGS. 13A, 13B and 13C). The human subject pulls theinput device 1306 backward (toward the positive X-Axis direction) whichmoves the enclosure 1302 and support 1304 forward (toward the negativeX-Axis direction) relative to the ground-contacting element 1310. Theposition of the center of gravity 1340 of the vehicle 1300 moves forwardin response to the enclosure 1302 and support 1304 moving forward. Aforward torque is generated by the ground-contacting element 1310 inresponse to the position of the center of gravity 1340 of the vehicle1300 moving forward. The human subject pushes the input device 1306forward (away from the human subject's body and along the negativeX-Axis direction) which moves the enclosure 1302 and support 1304backward (toward the positive X-Axis direction) relative to theground-contacting element 1310. The position of the center of gravity1340 of the vehicle 1300 moves backward in response to the enclosure1302 and support 1304 moving backward. A backward torque is generated bythe ground-contacting element 1310 in response to the position of thecenter of gravity 1340 of the vehicle 1300 moving backward.

FIG. 12A is a schematic illustration of a vehicle 1400, according to anillustrative embodiment of the invention. The vehicle 1400 includes anenclosure 1402 coupled to a platform 1412. The vehicle 1400 alsoincludes at least one ground-contacting element 1410 coupled to theplatform 1412. The ground-contacting element 1410 rotates about an axle1414. A structure (combination of rail 1416 and rail guide 1418) couplesthe support 1404 to the combination of the platform 1412, enclosure 1402and ground-contacting element 1410. A support 1404 is coupled to a rail1416. The support 1404 and rail 1416 slide relative to a rail guide 1418that is coupled to the platform 1412. In some embodiments, the railguide 1418 is instead coupled to the enclosure 1402.

In this embodiment, a human subject (not shown) manipulates an inputdevice 1406 to cause the position of the center of gravity 1440 of thevehicle 1400 to change. The input device 1406 is coupled to a linkage1408. The linkage 1408 is coupled to the support 1404. The human subjectpushes the input device 1406 forward (toward the negative X-Axisdirection) which moves the support 1404 forward (toward the negativeX-Axis direction) relative to the enclosure 1402, the platform 1412 andthe ground-contacting element 1410. The position of the center ofgravity 1440 of the vehicle 1400 moves forward in response to thesupport 1404 moving forward. A forward torque is generated by theground-contacting element 1410 in response to the center of gravity 1440of the vehicle 1400 moving forward. The human subject pulls the inputdevice 1406 backward (toward the human subject's body and along thepositive X-Axis direction) which moves the support 1404 backward (towardthe positive X-Axis direction) relative to the enclosure 1402, theplatform 1412 and the ground-contacting element 1410. The position ofthe center of gravity 1440 of the vehicle 1400 moves backward inresponse to the enclosure 1402 and support 1404 moving backward. Anegative torque is generated by the ground-contacting element 1410 inresponse to the position of the center of gravity 1440 of the vehicle1400 moving backward.

FIG. 12B is a schematic illustration of the vehicle 1400, according toan illustrative embodiment of the invention. The enclosure 1402 iscoupled to the platform 1412. The at least one ground-contacting element1410 is coupled to the platform 1412. The ground-contacting element 1410rotates about the axle 1414. A structure (the pivot member 1420) couplesthe support 1402 to the platform 1412, enclosure 1402 andground-contacting element 1410. The support 1404 is coupled to a pivotmember 1420 with a pivot mechanism 1422 located at a first end 1448 ofthe pivot member 1420. The pivot member 1420 is coupled to the platform1412 at a second end 1444 of the pivot member 1420. The support 1404pivots about the pivot mechanism (around the Z-Axis).

In this embodiment, a human subject (not shown) manipulates an inputdevice 1406 to cause the position of the center of gravity of thevehicle 1400 to change. The input device 1406 is coupled to the linkage1408. The linkage 1408 is coupled to the support 1404. The human subjectpushes the input device 1406 forward (toward the negative X-Axisdirection) which moves the support 1404 forward (toward the negativeX-Axis direction) relative to the enclosure 1402, the platform 1412 andthe ground-contacting element 1410. The position of the center ofgravity 1440 of the vehicle 1400 moves forward in response to thesupport 1404 moving forward. A forward torque is generated by theground-contacting element 1410 in response to the position of the centerof gravity 1440 of the vehicle 1400 moving forward. The human subjectpulls the input device 1406 backward (toward the human subject's bodyand along the positive X-Axis direction) which moves the support 1404backward (toward the positive X-Axis direction) relative to theenclosure 1402, the platform 1412 and the ground-contacting element1410. The position of the center of gravity 1440 of the vehicle 1400moves backward in response to the pivot member 1420 and support 1404moving backward. A negative torque is generated by the ground-contactingelement 1410 in response to the position of the center of gravity of thevehicle 1400 moving backward.

FIG. 12C is a schematic illustration of the vehicle 1400, according toan illustrative embodiment of the invention. The enclosure 1402 iscoupled to the platform 1412. The at least one ground-contacting element1410 is coupled to the platform 1412. The ground-contacting element 1410rotates about the axle 1414. The support 1404 is coupled to at least onefour-bar linkage 1424 (first bar 1424 a and second bar 1424 b). A firstend 1452 a of the first bar 1424 a is coupled to the support 1304. Asecond end 1456 a of the first bar 1424 a is coupled to the platform1412. A first end 1452 b of the second bar 1424 b is coupled to thesupport 1404. A second end 1456 b of the second bar 1424 b is coupled tothe platform 1412.

The support 1404 movies along a path 1460 defined by a rotation of thefour-bar linkage 1424 about the axle 1414 of the ground-contactingelement 1410 in the X-Y plane. In this embodiment, a human subject (notshown) manipulates an input device 1406 to cause the position of thecenter of gravity of the vehicle 1400 to change. The input device 1406is coupled to the linkage 1408. The linkage 1408 is coupled to thesupport 1404. The human subject pushes the input device 1406 forward(toward the negative X-Axis direction) which moves the enclosure 1402and support 1404 forward (toward the negative X-Axis direction) relativeto the enclosure 1402, the platform 1412 and the ground-contactingelement 1410. The position of the center of gravity 1440 of the vehicle1400 moves forward in response to the support 1404 moving forward. Aforward torque is generated by the ground-contacting element 1410 inresponse to the position of the center of gravity 1440 of the vehicle1400 moving forward. The human subject pulls the input device 1406backward (toward the human subject's body and along the positive X-Axisdirection) which moves the enclosure 1402 and support 1404 backward(toward the positive X-Axis direction) relative to the enclosure 1402,the platform 1412 and the ground-contacting element 1410. The positionof the center of gravity 1440 of the vehicle 1400 moves backward inresponse to the support 1404 moving backward. A negative torque isgenerated by the ground-contacting element 1410 in response to theposition of the center of gravity 1440 of the vehicle 1400 movingbackward.

In some embodiments, the vehicle 1400 includes two laterally disposedground-contacting elements. The vehicle also includes two four-barlinkages (e.g., two of the four-bar linkages 1424). Each four-barlinkage is coupled to one of the two laterally disposedground-contacting elements, similarly as described with respect to FIG.12C.

In some embodiments, one or more four-bar linkages are flexible bars.The flexible bars bend to permit, for example, the enclosure and supportto move along a path (e.g., the path 1460 of FIG. 12C).

FIG. 12D is a schematic illustration of a vehicle 1400, according to anillustrative embodiment of the invention. The enclosure 1402 is coupledto the platform 1412. The ground-contacting element 1410 is coupled tothe platform 1412. The ground-contacting element 1410 rotates about theaxle 1414. A structure (combination of rail 1416 and rail guide 1418)couples the support 1404 to the platform 1412, enclosure 1402 andground-contacting element 1410. The support 1404 is coupled to the rail1416. The support 1404 and rail 1416 slide relative to the rail guide1418 that is coupled to the platform 1410.

In this embodiment, a human subject (not shown) manipulates an inputdevice 1406 to cause the center of gravity 1440 of the vehicle 1400 tochange. This embodiment lacks a linkage (e.g., the linkage 1408 of FIGS.14A, 14B and 14C). The human subject pushes the input device 1406forward (toward the negative X-Axis direction) which moves the support1404 backward (toward the positive X-Axis direction) relative to theenclosure 1402, the platform 1412 and the ground-contacting element1410. The position of the center of gravity 1440 of the vehicle 1400moves backward in response to the support 1404 moving backward. Areverse torque is generated by the ground-contacting element 1410 inresponse to the position of the center of gravity 1440 of the vehicle1400 moving backward. The human subject pulls the input device 1406backward (toward the human subject's body and along the positive X-Axisdirection) which moves the support 1404 forward (toward the negativeX-Axis direction) relative to the enclosure 1402, the platform 1412 andthe ground-contacting element 1410. The position of the center ofgravity 1440 of the vehicle 1400 moves forward in response to thesupport 1404 moving forward. A forward torque is generated by theground-contacting element 1410 in response to the position of the centerof gravity of the vehicle 1400 moving forward.

In some embodiments, the support (e.g., support 1404 of FIG. 12A) movesrelative to the enclosure (e.g., enclosure 1402 of FIG. 12A). Theenclosure is constructed so that the support moves within the enclosureto create an effective change in position of center of gravity of thevehicle.

In some embodiments, the support (e.g., support 1304 of FIG. 11A) andthe enclosure (e.g., enclosure 1302 of FIG. 11A) are coupled togetherand, in combination, move relative to the ground-contacting element(e.g., ground-contacting element 1310 of FIG. 11A) to create aneffective change in position of center of gravity of the vehicle.Because the support and enclosure move together, the interior volume ofthe enclosure can be made less than would otherwise be necessary toaccommodate movement of the support within the enclosure. In someembodiments, the vehicle includes a seat belt (or other human subject orpayload restraint). Because the support and enclosure move together, theseat belt can be anchored to the enclosure. If the support movedrelative to the enclosure, the seat belt assembly would need to bedesigned to accommodate the movement of the support relative to theenclosure to insure that the seat belt still accomplished its role toprotect the payload or human subject disposed on the support.

In some embodiments, the linkage (e.g., the linkage 1308 of FIGS. 11A,11B and 11C or the linkage 1408 of FIGS. 12A, 12B and 12C) has a linkageratio that is adjustable. In some embodiments, the adjustable linkageratio is set (e.g., by a user, the manufacturer or by a vehicle module)to vary vehicle control stiffness, response and/or feel.

In some embodiments, the vehicle has a support that supports more thanone human subject. In some embodiments, the vehicle can be controlled byeither human subject.

In some embodiments, the vehicle has an input device that is a footrest.Human subject motion of the footrest causes the position of the centerof gravity of the vehicle to change. In some embodiments, the footrestis coupled to the platform of the vehicle by a linkage and movement ofthe footrest away from the human subject causes the position of thecenter of gravity to move backward relative to the ground-contactingelements. In some embodiments, the input device includes both a controlyoke and a footrest and movement of the control yoke and footrest awayfrom the human subject causes the position of the center of gravity tomove backward and movement of the control yoke and footrest towards thehuman subject causes the position of the center of gravity to moveforward.

In some embodiments, the change in the position of a center of gravityof a vehicle results in an equal, lesser or greater change in the torqueapplied to a) one or more ground-contacting elements of the vehicle orb) commanded velocity of the vehicle. For example, the change in torqueapplied to a ground-contacting element can have a non-linearrelationship (e.g., quadratic) relationship to the change in theposition of the center of gravity of the vehicle. In one embodiment, thenon-linear relationship amplifies the effect of the change in theposition of the center of gravity for an experienced human subjectand/or reduces the effect of the change in the position of the center ofgravity for an inexperienced human subject.

In some embodiments, a small motion (i.e., change of position of thecenter of gravity) creates a relatively level platform of the vehiclewith moderate acceleration or deceleration. In some embodiments, a largemotion (i.e. change of position of the center of gravity) creates alarge change in pitch of the vehicle and high rate or acceleration ordeceleration.

In some embodiments, the effect of the change in the position of thecenter of gravity is changed by, for example, adding or subtracting avehicle pitch-related parameter to a command signal provided to one ormore ground-contacting elements.

In some embodiments, an actuator coupled to a portion of the vehiclechanges the position of the center of gravity of the vehicle. Forexample, in some embodiments, the actuator is coupled to a movingcomponent of the vehicle (e.g., the support 1404 of FIG. 12D) and thevehicle has an input device that is coupled (e.g., wired or wirelessly)to the actuator. Motion of the input device commands the actuator tomove, which causes the support to move relative to the ground-contactingelements of the vehicle. Movement of the support forward relative to theground-contacting elements causes the position of the center of gravityof the vehicle to move forward which causes the vehicle to move forward.In some embodiments, the vehicle is not used to support a human subjectand the actuator can be used to command a change in the position of thecenter of gravity of the vehicle.

In some embodiments, the actuator includes a locking out mechanism thatinhibits a change in the center of gravity of the vehicle. For example,in an alternative embodiment of the invention described with respect toFIG. 11A, the vehicle 1300 includes an actuator with a locking outmechanism. The locking out mechanism limits or prevents motion of therail 1316 coupled to the support 1304 relative to the rail guide 1318coupled to the platform 1312. The locking out mechanism could be a pinin the rail 1316 that is inserted into one or a plurality ofcorresponding apertures located in the rail guide 1318. The locking outmechanism could be a brake (friction or disk break) coupled to the rail1316 and rail guide 1318. In some embodiments, the locking out mechanismincludes one or more mechanical stops coupled to the rail 1316 and railguide 1318. In some embodiments, the one or more mechanical stops engagein response to a predefined condition (e.g., rapid deceleration of thevehicle). The mechanical stop can be triggered if an emergency shut downof the vehicle 1300 is required.

FIGS. 13A and 13B are three-dimensional views of a vehicle 1500,according to illustrative embodiments of the invention. A human subject(not shown) rests on a support 1502 in an enclosure 1504 that at leastpartially encloses the human subject. The vehicle 1500 includes at leastthree ground-contacting elements 1508, 1510, 1520. The threeground-contacting elements 1508, 1510, 1520 are coupled to a platform1506. The ground-contacting element 1520 is a stabilizerground-contacting element.

The ground-contacting elements 1508, 1510 are laterally disposedrelative to each other and rotate about an axle 1514. Ground-contactingelement 1508 is powered by a drive 1516 and ground-contacting element1510 is powered by a drive (not shown for clarity of illustrationpurposes). The third ground-contacting element 1520 is disposed towardthe front of the platform 1506 (positioned toward the negative X-axisdirection relative to the two ground-contacting elements 1508 and 1510).The third ground-contacting element 1520 rotates about an axle 1522. Inan alternative embodiment, the ground-contacting elements 1508, 1510 arecoupled to the platform 1506 and ground-contacting element 1520 iscoupled to the enclosure 1504.

With respect to FIG. 13A, when the vehicle 1500 is balanced, the thirdground-contacting is nominally positioned such that the thirdground-contacting element 1520 does not touch the ground when thevehicle 1500 is in an upright position and the platform 1506 is parallelwith the ground. As shown in FIG. 13B, when the vehicle 1500 is notbalanced, the vehicle 1500 tips forward to rest on the thirdground-contacting element 1520 providing static stability of the vehicle1500.

In some embodiments, the third ground-contacting element 1520 includes awheel, skid, ball or post. In an alternative embodiment, the thirdground-contacting element 1520 is disposed toward the rear of theplatform 1506, such that the vehicle 1500 tips backward to rest on thethird ground-contacting element 1520. In some embodiments, it isdesirable for the third ground-contacting element 1520 to be locatedtoward the rear of the vehicle 1500. In situations where it is desirableto stop very quickly, for example, if an emergency stop is triggered,placement of the third ground-contacting element 1520 towards the rearof the platform 1506 helps ensure that a rearward portion of the vehicle1500 does not touch the ground while stopping and instead rests on thethird ground-contacting element 1520. While a deceleration torque isapplied to the two laterally disposed ground-contacting elements 1508,1510, the third ground-contacting element 1520 stabilizes the vehicle1500.

In some embodiments, there is a fourth ground-contacting element (notshown) and both the third ground-contacting element 1520 and the fourthground-contacting element are positioned toward the front of the vehicle1500 (toward the negative X-axis direction relative to the twoground-contacting elements 1508 and 1510). The third ground-contactingelement 1520 and the fourth ground-contacting element are laterallydisposed relative to each other to provide additional lateral stabilityto the vehicle 1500 when the third ground-contacting element 1520 andfourth ground-contacting element are in contact with the ground. In someembodiments, the third ground-contacting element 1520 and the fourthground-contacting element are disposed toward the rear of the platform.

In some embodiments, each of the ground-contacting elements 1508, 1510and 1520 are coupled to one or more motor drives allowing for positiveor negative torque to be applied to any of the ground-contactingelements 1508, 1510, 1520.

In various embodiments, the third ground-contacting element 1520 isretractable. The retractable third ground-contacting element 1520 isdeployed and retracted, for example, by an actuator attached to thevehicle 1500. In some embodiments, the third ground-contacting elementis linked to an input device (e.g., input device 1306 or 1406, asdiscussed above). Motion of the input device, can cause the thirdground-contacting element 1520 to be extended or refracted. In someembodiments, the third ground-contacting element 1520 includes a breakto at least assist with decelerating the vehicle 1500.

In some embodiments, the vehicle 1500 includes an input device andlinkage (e.g., input device 1306 and linkage 1308 of FIG. 11A). When thevehicle 1500 is tilted forward (tilted toward the negative X-axisdirection) it rests on the third ground-contacting element 1520. Becausethe input device is coupled to the linkage, the input device is locatedtowards the front of the vehicle 1500 (towards the negative X-axisdirection), locating the input device in a position within the enclosurethat makes it easier for a human subject to mount and dismount (enter orexit) the vehicle 1500.

In some embodiments, the portion of the support 1502 on which a humansubject would sit (or a payload would be located) is parallel to theground plane when the vehicle 1500 rests on the third ground-contactingelement 1520. Because the portion of the support 1502 on which the humansubject would sit is parallel to the ground plane, it is easier for thehuman subject to mount or dismount (enter or exit) the vehicle 1500.When the vehicle 1500 tips backward in to balancing mode, the portion ofthe support 1502 on which a human subject would sit (or a payload wouldbe located) is tipped backward creating a comfortable reclined positionfor the human subject (or a position that assists with securing thepayload).

A controller 1560 (e.g., the controller 1200 of FIG. 10, is coupled tothe drive 1516 for providing a control signal in response to changes ina position of a center of gravity 1512 of the vehicle 1500. In oneembodiment, the controller 1560 operates in, at least, a start mode,dynamic stabilization mode and a stop mode. The vehicle 1500 isinitially supported by each of the three ground-contacting elements1508, 1510 and 1520 in the off mode.

The human subject mounts the vehicle 1500 in the off state. The vehicleis turned on and the start mode is triggered by a change in the positionof the center of gravity 1512 of the vehicle 1500. In this embodiment,the human subject moves the center of gravity 1512 backward (toward thepositive X-Axis direction) triggering the start mode. During the startmode, the center of gravity 1512 moves backward (as, for examplecommanded by the human subject) until the third ground-contactingelement 1520 does not contact the ground.

When the third ground-contacting element 1520 is no longer in contactwith the ground, the dynamic stabilization mode is triggered and thevehicle 1500 is balanced on the two laterally disposed ground-contactingelements 1508 and 1510. The human subject then operates the vehicle 1500similarly as described herein.

In this embodiment, the stop mode is triggered by an operator issuing acommand to the controller 1560 (e.g., depressing a button or pushing atouch pad screen coupled to the controller). The vehicle 1500 tipsforward to rest on the third ground-contacting element 1520 in responseto the triggering of the stop mode.

In some embodiments, the stop mode is triggered by a predeterminedchange in the position of the center of gravity of the vehicle 1500. Ifthe human subject moves the center of gravity 1512 forward (toward thenegative X-Axis direction) beyond a predetermined center of gravitythreshold, the stop mode is triggered. The vehicle 1500 decelerates to acomplete stop before tipping forward to rest on the thirdground-contacting element 1520. Alternatively, the vehicle 1500 canstart tipping forward as the vehicle decelerates and the thirdground-contacting element 1520 comes in to contact with the ground whenthe vehicle reaches a predetermined (e.g., safe) speed.

Various embodiments exist for triggering and operating the variousoperating modes of the vehicle 1500. For example, the start and/or stopmode can be specified by the human subject via an input device (e.g.,handheld or vehicle mounted processor). In some embodiments, a humansubject or user initiates the dynamic stabilization mode. The center ofgravity threshold for the start and/or stop mode can be human subjectspecified or determined by the controller 1560 based on the experiencelevel of the human subject and/or based on a center of gravity positionstored the last time the vehicle 1500 was operated.

Some embodiments of the invention include additional operating modes. Insome embodiments, the vehicle 1500 includes a position-keeping mode inwhich the vehicle 1500 is balanced and nominally positioned in onelocation relative to the ground plane. While operating inposition-keeping mode, the sensitivity of the vehicle 1500 to changes inthe position of the center of gravity of the vehicle 1500 is increasedto allow the vehicle to remain balanced and nominally positioned in onelocation to create a stable riding experience for a human subject whilethe vehicle 1500 is, for example, stopped (e.g., at a red light). Thevehicle 1500 maintains its balance and stays still even if there areperturbations (e.g., small or large) to the position of the center ofgravity of the vehicle 1500 by causing a pitch of the vehicle in adirection opposite to the perturbation of the center of gravity.

In one embodiment, the position-keeping mode is an operating mode thevehicle 1500 enters when the velocity of the ground-contacting elements1508 and 1510 are below a predetermined threshold, the yaw velocity ofthe ground-contacting elements 1508 and 1510 are below a predeterminedthreshold, and the position of the center of gravity 1512 is below athreshold. Exit from the position-keeping mode is triggered when any ofthese parameters exceed the same (or different) thresholds.

In one embodiment of the invention, the vehicle 1500 enters aposition-keeping mode when the following conditions are present 1) theaverage velocity of the left and right ground-contacting elements 1508and 1510 is less than 0.7 MPH (0.313 m/s); 2) yaw velocity of thevehicle is less than 20 degrees/second; 3) velocity of the shaftattached to the left ground-contacting element 1508 is less than 0.7 MPH(0.313 m/s); 4) velocity of the shaft attached to the rightground-contacting element 1508 is less than 0.7 MPH (0.313 m/s); 5) theposition of the support 1502 relative to a predefined neutral positionalong the X-Axis is within 0.5 inches (12.7 mm) in the forwarddirection; 6) the position of the support 1502 relative to a predefinedneutral position along the X-Axis is within 1.5 inches (38.1 mm) in therearward direction; 7) the pitch of the vehicle is less than 4.0 degreesfrom a predefined neutral orientation; and 8) the pitch rate value isless than 15.0 degrees/second.

In one embodiment, the vehicle 1500 exits the position-keeping mode whenat least one of the following conditions is present 1) the position ofthe support 1502 relative to a predefined neutral position along theX-Axis is greater than 1.25 inches (31.8 mm) in the forward direction;2) the position of the support 1502 relative to a predefined neutralposition along the X-Axis is greater than 2.5 inches (63.5 mm) in therearward direction; 3) velocity of the shaft attached to the leftground-contacting element 1508 is greater than 1.5 MPH (0.671 m/s); or4) velocity of the shaft attached to the right ground-contacting element1508 is greater than 1.5 MPH (0.671 m/s).

In some embodiments, the vehicle 1500 includes static and dynamic modes.In one embodiment, the vehicle is balancing and is operating in a staticmode, the controller 1560 is operating a one-sided pitch controllerwhich does not allow rearward pitch of the vehicle 1500, so that thevehicle 1500 only moves backward if the position of the center ofgravity of the vehicle is moved backward. If the position of the centerof gravity is moved forward, the controller 1560 allows forward pitch ofthe vehicle 1500 until the stabilizer ground-contacting element 1520contacts the ground. In some embodiments, the vehicle is balancing andthe controller 1560 is configured to operate in a static mode thatignores a request to trigger the stop mode until the vehicle 1500 ismoving below a predetermined speed and/or acceleration. In someembodiments, the controller 1560 is configured so that the vehicle 1500does not immediately respond to initiate rearward movement of thevehicle after a quick stop of the vehicle 1500. The vehicle 1500 can becommanded to respond in this manner by, for example, pitching thevehicle forward as it comes to a stop or by commanding an actuator tovary the position of the center of gravity of the vehicle (e.g.,commanding an actuator to move the support and enclosure relative to theground-contacting elements).

In some embodiments, input from the human subject is ignored during thestart and/or stop mode to avoid unintended motion of the vehicle 1500.In one embodiment, the vehicle 1500 has a smoothing function thatsmoothly transitions from the start mode to the dynamic stabilizationmode to be comfortable for the human subject. For example, in oneembodiment, the smoothing function includes a low pass filter thatfilters out high frequency motions (e.g., jittery human subjectcommands) as the vehicle transitions from start mode to the dynamicstabilization mode.

Various embodiments exist for detecting trigger commands (e.g., startand/or stop mode triggers). In one embodiment, a force sensor coupled tothe third ground-contacting element 1520 detects contact of the thirdground-contacting element 1520 with the ground or a position sensor(contact or non-contact position sensor) detects a position of the thirdground-contacting element 1520 relative to, for example, the ground or astationary location on the vehicle 1500. In some embodiments, thecontroller senses pitch and/or pitch rate of the vehicle 1500 to enabledynamic stabilization or the stop mode based on, for example, a rategyro sensor.

In some embodiments, the controller 1560 compensates for unintendedcontact of the third ground-contacting member 1520 with the ground whilethe vehicle is dynamically stabilized. For example, during uphilltravel, the platform 1506, enclosure 1504 and support 1502 can pitchforward to maintain an upright position (relative to an earth verticalaxis) of the human subject. A third ground-contacting element 1520 thatis not retractable and which is positioned toward the front of theplatform 1506 unintentionally contacts the ground because the vehicle1500 pitches forward. The unintentional ground contact of the thirdground-contacting element 1520 creates a force on the vehicle 1500causing an unintentional change in the position of the center of gravity1512. As discussed above, a change in the position of the center ofgravity 1512 accelerates or decelerates the vehicle 1500. In thismanner, the controller 1560 can be configured to sense the contact ofthe third ground-contacting element 1520 with the ground and ignore achange in the position of the center of gravity 1512 which isproportional to the force exerted by the ground on the thirdground-contacting element 1520. This compensates for the unintendedcontact of the third ground-contacting element 1520 with the ground.

In further embodiments of the invention, a remote control is used tooperate the vehicle 1500. The remote control is used to vary theposition of the center of gravity 1512 by, for example, an operatorcommanding a change to a pitch of the vehicle 1500 or controlling anactuated center of gravity shifting mechanism to cause the position ofthe center of gravity 1512 of the vehicle 1500 to change. In oneembodiment, the center of gravity shifting mechanism can be disabled bybeing locked. In other embodiments, the remote control controls thethree ground-contacting elements 1508, 1510, 1520, such that the vehicle1500 may be commanded to move on all three ground-contacting elements1508, 1510, 1520. Torque commands can be provided to one or more of theground-contacting element 1508, 1510 and 1520. Additionally, the remotecontrol can disable the vehicle's 1500 response to a change in theposition of the center of gravity 1512.

FIG. 14 is a schematic illustration of a vehicle 1600, according to anillustrative embodiment of the invention. The vehicle 1600 includes anenclosure 1602 coupled to a support 1604. The vehicle 1600 also includesat least one ground-contacting element 1610 coupled to a platform 1612.The ground-contacting element 1610 rotates about an axle 1614 which iscoupled to the platform 1612. The vehicle 1600 includes a first drive1672 (combination of drive component 1672 a and drive component 1672 b).The first drive 1672 allows for movement of the enclosure 1602 andsupport 1604 (coupled to drive component 1672 a) relative to theground-contacting element 1610 and platform 1612 (coupled to the drivecomponent 1672 b). A control system (e.g., the control system 1200 ofFIG. 10) coupled to the first drive 1672 controls balancing of thevehicle 1600 in response to the position of the enclosure 1602 andsupport 1604 (coupled to drive component 1672 a) relative to theground-contacting element 1610 and platform 1612 (coupled to the drivecomponent 1672 b). In some embodiments, the first drive 1672 iselectrically actuated to maintain the position of the center of gravity1640 of the vehicle 1600 above the location that the ground-contactingelement 1610 contacts the ground to maintain balance of the vehicle inthe fore-aft direction.

The vehicle 1600 also includes a second drive 1680 coupled to theplatform 1612 and the ground-contacting element 1610. The second drive1680 (e.g., a motorized drive) delivers power to the ground-contactingelement 1610 to cause rotation of the ground-contacting element to movethe vehicle fore (towards the negative X-Axis direction) and aft(towards the positive X-Axis direction). The second drive can include,for example, an internal combustion engine, pedal or crank coupled tothe second drive for delivering power to the ground-contacting elements.In some embodiments, the vehicle 1600 includes two or more laterallydisposed ground-contacting elements 1610 which assist with providinglateral stability to the vehicle 1600.

The vehicle 1600 includes an input device 1606. A human subject (notshown) manipulates the input device 1306 to command the second drive1680 to command rotation of the ground-contacting element 1610 to movethe vehicle in the fore and aft directions.

In various embodiments, the disclosed methods can be implemented as acomputer program product for use with a computer system. Suchimplementations can include a series of computer instructions fixedeither on a tangible medium, such as a computer readable medium (e.g., adiskette, CD-ROM, ROM, or fixed disk) or transmittable to a computersystem, via a modem or other interface device, such as a communicationsadapter connected to a network over a medium. The medium can be either atangible medium (e.g., optical or analog communications lines) or amedium implemented with wireless techniques (e.g., microwave, infraredor other transmission techniques). The series of computer instructionsembodies all or part of the functionality previously described hereinwith respect to the system. Those skilled in the art should appreciatethat such computer instructions can be written in a number ofprogramming languages for use with many computer architectures oroperating systems.

Furthermore, such instructions can be stored in any memory device, suchas semiconductor, magnetic, optical or other memory devices, and can betransmitted using any communications technology, such as optical,infrared, microwave, or other transmission technologies. It is expectedthat such a computer program product can be distributed as a removablemedium with accompanying printed or electronic documentation (e.g.,shrink wrapped software), preloaded with a computer system (e.g., onsystem ROM or fixed disk), or distributed from a server or electronicbulletin board over the network (e.g., the Internet or World Wide Web).Of course, some embodiments of the invention can be implemented as acombination of both software (e.g., a computer program product) andhardware. Still other embodiments of the invention are implemented asentirely hardware, or entirely software (e.g., a computer programproduct).

The described embodiments of the invention are intended to be merelyexemplary and numerous variations and modifications will be apparent tothose skilled in the art. All such variations and modifications areintended to be within the scope of the present invention as defined inany appended claims.

1. (canceled)
 2. A vehicle for transporting a payload over a surface,the vehicle comprising: a support for supporting a payload; an enclosurefor at least partially enclosing the payload; two laterally disposedground-contacting elements coupled to at least one of the enclosure orthe support; a drive coupled to the ground-contacting elements; and acontroller coupled to the drive, for governing the operation of thedrive at least in response to position of the center of gravity of thevehicle to dynamically control balancing of the vehicle by moving theground-contacting elements fore and aft of the vehicle.
 3. The vehicleof claim 2, comprising a second drive for delivering power to theground-contacting elements to propel the vehicle fore and aft.
 4. Thevehicle of claim 2, wherein the drive is a motorized drive.
 5. Thevehicle of claim 2, wherein the controller coupled to the drive, governsthe operation of the drive at least in response to pitch of the vehicleto dynamically control balancing of the vehicle.
 6. The vehicle of claim2, comprising a structure coupling the support and the enclosure to theground-contacting elements, the structure allows for variation in theposition of the center of gravity.
 7. The vehicle of claim 6, whereinthe structure includes rails allowing the enclosure and support to slidewith respect to the ground-contacting elements.
 8. The vehicle of claim6, wherein the structure includes a pivot mechanism coupling the supportand enclosure to the ground-contacting elements allowing the enclosureand support to pivot with respect to the ground-contacting elements. 9.The vehicle of claim 2, wherein the payload is a human subject and thevehicle includes an input device, the human subject pushes or pulls theinput device allowing the human subject, support and enclosure to movewith respect to the ground-contacting elements.
 10. A method fortransporting a payload over a surface with a vehicle, the methodcomprising: supporting a payload with a support; at least partiallyenclosing the support with an enclosure; and controlling operation of adrive coupled to two laterally disposed ground-contacting elements,coupled to at least one of the enclosure or support, in response toposition of the center of gravity of the vehicle to dynamically controlbalancing of the vehicle by moving the ground contacting elements foreand aft of the vehicle.
 11. The method of claim 10, comprisingdelivering power from the drive to the ground-contacting elements tomove the ground-contacting elements fore and aft of the vehicle.
 12. Themethod of claim 11, wherein the delivered power is in response toattitude of the vehicle.
 13. The method of claim 10, comprisingdelivering power from a second drive to the ground-contacting elementsto cause rotation of the ground-contacting elements to move the vehiclefore and aft.
 14. The method of claim 10, wherein the enclosure iscoupled to the support and the support and enclosure move relative tothe ground-contacting elements to change the position of the center ofgravity of the vehicle.
 15. The method of claim 10, wherein theenclosure is coupled to the ground-contacting elements and the supportmoves relative to the enclosure and ground-contacting elements to changethe position of the center of gravity of the vehicle.
 16. A vehicle fortransporting a payload over a surface, the vehicle comprising: a supportfor supporting a payload; an enclosure for at least partially enclosingthe payload; two laterally disposed ground-contacting elements coupledto at least one of the enclosure or the support; a first drive coupledto the ground-contacting elements; a controller coupled to the firstdrive, for governing the operation of the first drive at least inresponse to position of the center of gravity of the vehicle to move theground-contacting elements fore and aft of the vehicle to dynamicallycontrol balancing of the vehicle; and a second drive coupled to theground-contacting elements to deliver power to the ground-contactingelements to propel the vehicle fore and aft.
 17. The vehicle of claim16, wherein the second drive dynamically controls balancing of thevehicle.
 18. The vehicle of claim 16, comprising an internal combustionengine coupled to the second drive for delivering power to theground-contacting elements.
 19. The vehicle of claim 16, comprisingrails coupled to the ground-contacting elements allowing the first driveto command the ground-contacting elements to move fore and aft of thevehicle to dynamically control balancing of the vehicle.
 20. A methodfor transporting a payload over a surface with a vehicle, the methodcomprising: supporting a payload with a support; at least partiallyenclosing the support with an enclosure; controlling operation of afirst drive coupled to two laterally disposed ground-contactingelements, coupled to at least one of the enclosure or support, inresponse to position of the center of gravity of the vehicle to move theground-contacting elements fore and aft of the vehicle to dynamicallycontrol balancing of the vehicle; and controlling operation of a seconddrive coupled to the two laterally disposed ground-contacting elementsto deliver power to the ground-contacting elements to propel the vehiclefore and aft.
 21. The vehicle of claim 20, wherein the second drivedynamically controls balancing of the vehicle.